From 1a038249967b51878bc492df42e24b2af797bb85 Mon Sep 17 00:00:00 2001 From: marha Date: Fri, 21 May 2010 06:36:23 +0000 Subject: xserver git update 21/5/2010 --- xorg-server/hw/dmx/doc/Makefile.am | 557 +++--- xorg-server/hw/dmx/doc/dmx.sgml | 2777 ----------------------------- xorg-server/hw/dmx/doc/dmx.xml | 3447 ++++++++++++++++++++++++++++++++++++ xorg-server/hw/dmx/doc/scaled.sgml | 707 -------- xorg-server/hw/dmx/doc/scaled.xml | 725 ++++++++ 5 files changed, 4439 insertions(+), 3774 deletions(-) delete mode 100644 xorg-server/hw/dmx/doc/dmx.sgml create mode 100644 xorg-server/hw/dmx/doc/dmx.xml delete mode 100644 xorg-server/hw/dmx/doc/scaled.sgml create mode 100644 xorg-server/hw/dmx/doc/scaled.xml (limited to 'xorg-server/hw/dmx/doc') diff --git a/xorg-server/hw/dmx/doc/Makefile.am b/xorg-server/hw/dmx/doc/Makefile.am index ef7c23da1..58cb27c17 100644 --- a/xorg-server/hw/dmx/doc/Makefile.am +++ b/xorg-server/hw/dmx/doc/Makefile.am @@ -1,290 +1,267 @@ -# Copyright 2005 Red Hat, Inc. -# -# Permission to use, copy, modify, distribute, and sell this software -# and its documentation for any purpose is hereby granted without -# fee, provided that the above copyright notice appear in all copies -# and that both that copyright notice and this permission notice -# appear in supporting documentation, and that the name of Red Hat -# not be used in advertising or publicity pertaining to distribution -# of the software without specific, written prior permission. Red -# Hat makes no representations about the suitability of this software -# for any purpose. It is provided "as is" without express or implied -# warranty. -# -# RED HAT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, -# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN -# NO EVENT SHALL RED HAT BE LIABLE FOR ANY SPECIAL, INDIRECT OR -# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS -# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, -# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN -# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. - -SGML_FILES = dmx.sgml scaled.sgml - -if BUILD_LINUXDOC -TXT_FILES = $(SGML_FILES:%.sgml=%.txt) -PS_FILES = $(SGML_FILES:%.sgml=%.ps) -if BUILD_PDFDOC -PDF_FILES = $(SGML_FILES:%.sgml=%.pdf) -endif -HTML_FILES = $(SGML_FILES:%.sgml=%.html) - -SUFFIXES = .sgml .txt .html .ps .pdf - -.sgml.txt: - @rm -f $@ - $(AM_V_GEN)$(MAKE_TEXT) $< - -.sgml.ps: - @rm -f $@ - $(AM_V_GEN)$(MAKE_PS) $< - -.ps.pdf: - @rm -f $@ - $(AM_V_GEN)$(MAKE_PDF) $< - -.sgml.html: - @rm -f $@ - $(AM_V_GEN)$(MAKE_HTML) $< - -noinst_DATA = $(TXT_FILES) $(PS_FILES) $(PDF_FILES) $(HTML_FILES) -CLEANFILES = $(TXT_FILES) $(PS_FILES) $(PDF_FILES) $(HTML_FILES) -endif - -if HAVE_DOXYGEN - -DOXYGEN_SRC=doxygen.head doxygen.foot doxygen.css doxygen.conf - -all-local: html/annotated.html - -dist-local: html/annotated.html - -html/annotated.html: $(DOXYGEN_SRC) - $(DOXYGEN) $(srcdir)/doxygen.conf - -maintainer-clean-local: - rm -rf html/ -endif - -EXTRA_DIST = \ - $(SGML_FILES) \ - DMXSpec.txt \ - DMXSpec-v1.txt \ - dmx.txt \ - doxygen.conf \ - doxygen.css \ - doxygen.foot \ - doxygen.head \ - scaled.txt \ - html/annotated.html \ - html/ChkNotMaskEv_8c.html \ - html/ChkNotMaskEv_8h.html \ - html/ChkNotMaskEv_8h_source.html \ - html/classes.html \ - html/dmx_8h.html \ - html/dmx_8h_source.html \ - html/dmxarg_8c.html \ - html/dmxarg_8h.html \ - html/dmxarg_8h_source.html \ - html/dmxbackend_8c.html \ - html/dmxbackend_8h.html \ - html/dmxbackend_8h_source.html \ - html/dmxcb_8c.html \ - html/dmxcb_8h.html \ - html/dmxcb_8h_source.html \ - html/dmxclient_8h.html \ - html/dmxclient_8h_source.html \ - html/dmxcmap_8c.html \ - html/dmxcmap_8h.html \ - html/dmxcmap_8h_source.html \ - html/dmxcommon_8c.html \ - html/dmxcommon_8h.html \ - html/dmxcommon_8h_source.html \ - html/dmxcompat_8c.html \ - html/dmxcompat_8h.html \ - html/dmxcompat_8h_source.html \ - html/dmxconfig_8c.html \ - html/dmxconfig_8h.html \ - html/dmxconfig_8h_source.html \ - html/dmxconsole_8c.html \ - html/dmxconsole_8h.html \ - html/dmxconsole_8h_source.html \ - html/dmxcursor_8c.html \ - html/dmxcursor_8h.html \ - html/dmxcursor_8h_source.html \ - html/dmxdetach_8c.html \ - html/dmxdpms_8c.html \ - html/dmxdpms_8h.html \ - html/dmxdpms_8h_source.html \ - html/dmxdummy_8c.html \ - html/dmxdummy_8h.html \ - html/dmxdummy_8h_source.html \ - html/dmxevents_8c.html \ - html/dmxevents_8h.html \ - html/dmxevents_8h_source.html \ - html/dmxextension_8c.html \ - html/dmxextension_8h.html \ - html/dmxextension_8h_source.html \ - html/dmxfont_8c.html \ - html/dmxfont_8h.html \ - html/dmxfont_8h_source.html \ - html/dmxgc_8c.html \ - html/dmxgc_8h.html \ - html/dmxgc_8h_source.html \ - html/dmxgcops_8c.html \ - html/dmxgcops_8h.html \ - html/dmxgcops_8h_source.html \ - html/dmx__glxvisuals_8h_source.html \ - html/dmxinit_8c.html \ - html/dmxinit_8h.html \ - html/dmxinit_8h_source.html \ - html/dmxinput_8c.html \ - html/dmxinput_8h.html \ - html/dmxinput_8h_source.html \ - html/dmxinputinit_8c.html \ - html/dmxinputinit_8h.html \ - html/dmxinputinit_8h_source.html \ - html/dmxlog_8c.html \ - html/dmxlog_8h.html \ - html/dmxlog_8h_source.html \ - html/dmxmap_8c.html \ - html/dmxmap_8h.html \ - html/dmxmap_8h_source.html \ - html/dmxmotion_8c.html \ - html/dmxmotion_8h.html \ - html/dmxmotion_8h_source.html \ - html/dmxparse_8c.html \ - html/dmxparse_8h.html \ - html/dmxparse_8h_source.html \ - html/dmxpict_8c.html \ - html/dmxpict_8h.html \ - html/dmxpict_8h_source.html \ - html/dmxpixmap_8c.html \ - html/dmxpixmap_8h.html \ - html/dmxpixmap_8h_source.html \ - html/dmxprint_8c.html \ - html/dmxprint_8h.html \ - html/dmxprint_8h_source.html \ - html/dmxprop_8c.html \ - html/dmxprop_8h.html \ - html/dmxprop_8h_source.html \ - html/dmxscrinit_8c.html \ - html/dmxscrinit_8h.html \ - html/dmxscrinit_8h_source.html \ - html/dmxshadow_8c.html \ - html/dmxshadow_8h.html \ - html/dmxshadow_8h_source.html \ - html/dmxsigio_8c.html \ - html/dmxsigio_8h.html \ - html/dmxsigio_8h_source.html \ - html/dmxstat_8c.html \ - html/dmxstat_8h.html \ - html/dmxstat_8h_source.html \ - html/dmxsync_8c.html \ - html/dmxsync_8h.html \ - html/dmxsync_8h_source.html \ - html/dmxvisual_8c.html \ - html/dmxvisual_8h.html \ - html/dmxvisual_8h_source.html \ - html/dmxwindow_8c.html \ - html/dmxwindow_8h.html \ - html/dmxwindow_8h_source.html \ - html/dmxxinput_8c.html \ - html/doxygen.css \ - html/doxygen.png \ - html/files.html \ - html/ftv2blank.png \ - html/ftv2doc.png \ - html/ftv2folderclosed.png \ - html/ftv2folderopen.png \ - html/ftv2lastnode.png \ - html/ftv2link.png \ - html/ftv2mlastnode.png \ - html/ftv2mnode.png \ - html/ftv2node.png \ - html/ftv2plastnode.png \ - html/ftv2pnode.png \ - html/ftv2vertline.png \ - html/functions.html \ - html/functions_vars.html \ - html/globals_defs.html \ - html/globals_enum.html \ - html/globals_eval.html \ - html/globals_func.html \ - html/globals.html \ - html/globals_type.html \ - html/globals_vars.html \ - html/index.html \ - html/lnx-keyboard_8c.html \ - html/lnx-keyboard_8h.html \ - html/lnx-keyboard_8h_source.html \ - html/lnx-ms_8c.html \ - html/lnx-ms_8h.html \ - html/lnx-ms_8h_source.html \ - html/lnx-ps2_8c.html \ - html/lnx-ps2_8h.html \ - html/lnx-ps2_8h_source.html \ - html/main.html \ - html/struct__dmxArg.html \ - html/struct__dmxColormapPriv.html \ - html/structDMXConfigCmdStruct.html \ - html/struct__DMXConfigComment.html \ - html/struct__DMXConfigDisplay.html \ - html/struct__DMXConfigEntry.html \ - html/struct__DMXConfigFullDim.html \ - html/structDMXConfigListStruct.html \ - html/struct__DMXConfigNumber.html \ - html/struct__DMXConfigOption.html \ - html/struct__DMXConfigPair.html \ - html/struct__DMXConfigParam.html \ - html/struct__DMXConfigPartDim.html \ - html/struct__DMXConfigString.html \ - html/struct__DMXConfigSub.html \ - html/struct__DMXConfigToken.html \ - html/struct__DMXConfigVirtual.html \ - html/struct__DMXConfigWall.html \ - html/struct__dmxCursorPriv.html \ - html/structDMXDesktopAttributesRec.html \ - html/struct__DMXEventMap.html \ - html/struct__dmxFontPriv.html \ - html/struct__dmxGCPriv.html \ - html/structdmxGlxVisualPrivate.html \ - html/struct__dmxGlyphPriv.html \ - html/structDMXInputAttributesRec.html \ - html/struct__DMXInputInfo.html \ - html/struct__DMXLocalInitInfo.html \ - html/struct__DMXLocalInputInfo.html \ - html/struct__dmxPictPriv.html \ - html/struct__dmxPixPriv.html \ - html/structDMXScreenAttributesRec.html \ - html/struct__DMXScreenInfo.html \ - html/struct__DMXStatAvg.html \ - html/struct__DMXStatInfo.html \ - html/structDMXWindowAttributesRec.html \ - html/struct__dmxWinPriv.html \ - html/struct__myPrivate.html \ - html/tree.html \ - html/usb-common_8c.html \ - html/usb-common_8h.html \ - html/usb-common_8h_source.html \ - html/usb-keyboard_8c.html \ - html/usb-keyboard_8h.html \ - html/usb-keyboard_8h_source.html \ - html/usb-mouse_8c.html \ - html/usb-mouse_8h.html \ - html/usb-mouse_8h_source.html \ - html/usb-other_8c.html \ - html/usb-other_8h.html \ - html/usb-other_8h_source.html \ - html/usb-private_8h.html \ - html/usb-private_8h_source.html - -$(builddir)/doxygen.head: - $(LN_S) $(srcdir)/doxygen.head $@ - -$(builddir)/doxygen.foot: - $(LN_S) $(srcdir)/doxygen.foot $@ - -$(builddir)doxygen.css: - $(LN_S) $(srcdir)/doxygen.css $@ - +# Copyright 2005 Red Hat, Inc. +# +# Permission to use, copy, modify, distribute, and sell this software +# and its documentation for any purpose is hereby granted without +# fee, provided that the above copyright notice appear in all copies +# and that both that copyright notice and this permission notice +# appear in supporting documentation, and that the name of Red Hat +# not be used in advertising or publicity pertaining to distribution +# of the software without specific, written prior permission. Red +# Hat makes no representations about the suitability of this software +# for any purpose. It is provided "as is" without express or implied +# warranty. +# +# RED HAT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, +# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN +# NO EVENT SHALL RED HAT BE LIABLE FOR ANY SPECIAL, INDIRECT OR +# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS +# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, +# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN +# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + +XML_FILES = dmx.xml scaled.xml + +include ../../../doc/xml/xmlrules.in + +if ENABLE_DEVEL_DOCS +noinst_DATA = $(BUILT_DOC_FILES) +endif +CLEANFILES = $(CLEAN_DOC_FILES) + +if HAVE_DOXYGEN + +DOXYGEN_SRC=doxygen.head doxygen.foot doxygen.css doxygen.conf + +all-local: html/annotated.html + +dist-local: html/annotated.html + +html/annotated.html: $(DOXYGEN_SRC) + $(DOXYGEN) $(srcdir)/doxygen.conf + +maintainer-clean-local: + rm -rf html/ +endif + +EXTRA_DIST = \ + $(XML_FILES) \ + DMXSpec.txt \ + DMXSpec-v1.txt \ + dmx.txt \ + doxygen.conf \ + doxygen.css \ + doxygen.foot \ + doxygen.head \ + scaled.txt \ + html/annotated.html \ + html/ChkNotMaskEv_8c.html \ + html/ChkNotMaskEv_8h.html \ + html/ChkNotMaskEv_8h_source.html \ + html/classes.html \ + html/dmx_8h.html \ + html/dmx_8h_source.html \ + html/dmxarg_8c.html \ + html/dmxarg_8h.html \ + html/dmxarg_8h_source.html \ + html/dmxbackend_8c.html \ + html/dmxbackend_8h.html \ + html/dmxbackend_8h_source.html \ + html/dmxcb_8c.html \ + html/dmxcb_8h.html \ + html/dmxcb_8h_source.html \ + html/dmxclient_8h.html \ + html/dmxclient_8h_source.html \ + html/dmxcmap_8c.html \ + html/dmxcmap_8h.html \ + html/dmxcmap_8h_source.html \ + html/dmxcommon_8c.html \ + html/dmxcommon_8h.html \ + html/dmxcommon_8h_source.html \ + html/dmxcompat_8c.html \ + html/dmxcompat_8h.html \ + html/dmxcompat_8h_source.html \ + html/dmxconfig_8c.html \ + html/dmxconfig_8h.html \ + html/dmxconfig_8h_source.html \ + html/dmxconsole_8c.html \ + html/dmxconsole_8h.html \ + html/dmxconsole_8h_source.html \ + html/dmxcursor_8c.html \ + html/dmxcursor_8h.html \ + html/dmxcursor_8h_source.html \ + html/dmxdetach_8c.html \ + html/dmxdpms_8c.html \ + html/dmxdpms_8h.html \ + html/dmxdpms_8h_source.html \ + html/dmxdummy_8c.html \ + html/dmxdummy_8h.html \ + html/dmxdummy_8h_source.html \ + html/dmxevents_8c.html \ + html/dmxevents_8h.html \ + html/dmxevents_8h_source.html \ + html/dmxextension_8c.html \ + html/dmxextension_8h.html \ + html/dmxextension_8h_source.html \ + html/dmxfont_8c.html \ + html/dmxfont_8h.html \ + html/dmxfont_8h_source.html \ + html/dmxgc_8c.html \ + html/dmxgc_8h.html \ + html/dmxgc_8h_source.html \ + html/dmxgcops_8c.html \ + html/dmxgcops_8h.html \ + html/dmxgcops_8h_source.html \ + html/dmx__glxvisuals_8h_source.html \ + html/dmxinit_8c.html \ + html/dmxinit_8h.html \ + html/dmxinit_8h_source.html \ + html/dmxinput_8c.html \ + html/dmxinput_8h.html \ + html/dmxinput_8h_source.html \ + html/dmxinputinit_8c.html \ + html/dmxinputinit_8h.html \ + html/dmxinputinit_8h_source.html \ + html/dmxlog_8c.html \ + html/dmxlog_8h.html \ + html/dmxlog_8h_source.html \ + html/dmxmap_8c.html \ + html/dmxmap_8h.html \ + html/dmxmap_8h_source.html \ + html/dmxmotion_8c.html \ + html/dmxmotion_8h.html \ + html/dmxmotion_8h_source.html \ + html/dmxparse_8c.html \ + html/dmxparse_8h.html \ + html/dmxparse_8h_source.html \ + html/dmxpict_8c.html \ + html/dmxpict_8h.html \ + html/dmxpict_8h_source.html \ + html/dmxpixmap_8c.html \ + html/dmxpixmap_8h.html \ + html/dmxpixmap_8h_source.html \ + html/dmxprint_8c.html \ + html/dmxprint_8h.html \ + html/dmxprint_8h_source.html \ + html/dmxprop_8c.html \ + html/dmxprop_8h.html \ + html/dmxprop_8h_source.html \ + html/dmxscrinit_8c.html \ + html/dmxscrinit_8h.html \ + html/dmxscrinit_8h_source.html \ + html/dmxshadow_8c.html \ + html/dmxshadow_8h.html \ + html/dmxshadow_8h_source.html \ + html/dmxsigio_8c.html \ + html/dmxsigio_8h.html \ + html/dmxsigio_8h_source.html \ + html/dmxstat_8c.html \ + html/dmxstat_8h.html \ + html/dmxstat_8h_source.html \ + html/dmxsync_8c.html \ + html/dmxsync_8h.html \ + html/dmxsync_8h_source.html \ + html/dmxvisual_8c.html \ + html/dmxvisual_8h.html \ + html/dmxvisual_8h_source.html \ + html/dmxwindow_8c.html \ + html/dmxwindow_8h.html \ + html/dmxwindow_8h_source.html \ + html/dmxxinput_8c.html \ + html/doxygen.css \ + html/doxygen.png \ + html/files.html \ + html/ftv2blank.png \ + html/ftv2doc.png \ + html/ftv2folderclosed.png \ + html/ftv2folderopen.png \ + html/ftv2lastnode.png \ + html/ftv2link.png \ + html/ftv2mlastnode.png \ + html/ftv2mnode.png \ + html/ftv2node.png \ + html/ftv2plastnode.png \ + html/ftv2pnode.png \ + html/ftv2vertline.png \ + html/functions.html \ + html/functions_vars.html \ + html/globals_defs.html \ + html/globals_enum.html \ + html/globals_eval.html \ + html/globals_func.html \ + html/globals.html \ + html/globals_type.html \ + html/globals_vars.html \ + html/index.html \ + html/lnx-keyboard_8c.html \ + html/lnx-keyboard_8h.html \ + html/lnx-keyboard_8h_source.html \ + html/lnx-ms_8c.html \ + html/lnx-ms_8h.html \ + html/lnx-ms_8h_source.html \ + html/lnx-ps2_8c.html \ + html/lnx-ps2_8h.html \ + html/lnx-ps2_8h_source.html \ + html/main.html \ + html/struct__dmxArg.html \ + html/struct__dmxColormapPriv.html \ + html/structDMXConfigCmdStruct.html \ + html/struct__DMXConfigComment.html \ + html/struct__DMXConfigDisplay.html \ + html/struct__DMXConfigEntry.html \ + html/struct__DMXConfigFullDim.html \ + html/structDMXConfigListStruct.html \ + html/struct__DMXConfigNumber.html \ + html/struct__DMXConfigOption.html \ + html/struct__DMXConfigPair.html \ + html/struct__DMXConfigParam.html \ + html/struct__DMXConfigPartDim.html \ + html/struct__DMXConfigString.html \ + html/struct__DMXConfigSub.html \ + html/struct__DMXConfigToken.html \ + html/struct__DMXConfigVirtual.html \ + html/struct__DMXConfigWall.html \ + html/struct__dmxCursorPriv.html \ + html/structDMXDesktopAttributesRec.html \ + html/struct__DMXEventMap.html \ + html/struct__dmxFontPriv.html \ + html/struct__dmxGCPriv.html \ + html/structdmxGlxVisualPrivate.html \ + html/struct__dmxGlyphPriv.html \ + html/structDMXInputAttributesRec.html \ + html/struct__DMXInputInfo.html \ + html/struct__DMXLocalInitInfo.html \ + html/struct__DMXLocalInputInfo.html \ + html/struct__dmxPictPriv.html \ + html/struct__dmxPixPriv.html \ + html/structDMXScreenAttributesRec.html \ + html/struct__DMXScreenInfo.html \ + html/struct__DMXStatAvg.html \ + html/struct__DMXStatInfo.html \ + html/structDMXWindowAttributesRec.html \ + html/struct__dmxWinPriv.html \ + html/struct__myPrivate.html \ + html/tree.html \ + html/usb-common_8c.html \ + html/usb-common_8h.html \ + html/usb-common_8h_source.html \ + html/usb-keyboard_8c.html \ + html/usb-keyboard_8h.html \ + html/usb-keyboard_8h_source.html \ + html/usb-mouse_8c.html \ + html/usb-mouse_8h.html \ + html/usb-mouse_8h_source.html \ + html/usb-other_8c.html \ + html/usb-other_8h.html \ + html/usb-other_8h_source.html \ + html/usb-private_8h.html \ + html/usb-private_8h_source.html + +$(builddir)/doxygen.head: + $(LN_S) $(srcdir)/doxygen.head $@ + +$(builddir)/doxygen.foot: + $(LN_S) $(srcdir)/doxygen.foot $@ + +$(builddir)doxygen.css: + $(LN_S) $(srcdir)/doxygen.css $@ + diff --git a/xorg-server/hw/dmx/doc/dmx.sgml b/xorg-server/hw/dmx/doc/dmx.sgml deleted file mode 100644 index 4342c2fce..000000000 --- a/xorg-server/hw/dmx/doc/dmx.sgml +++ /dev/null @@ -1,2777 +0,0 @@ - -
- - - Distributed Multihead X design - <author>Kevin E. Martin, David H. Dawes, and Rickard E. Faith - <date>29 June 2004 (created 25 July 2001) - <abstract> - This document covers the motivation, background, design, and - implementation of the distributed multihead X (DMX) system. It - is a living document and describes the current design and - implementation details of the DMX system. As the project - progresses, this document will be continually updated to reflect - the changes in the code and/or design. <it>Copyright 2001 by VA - Linux Systems, Inc., Fremont, California. Copyright 2001-2004 - by Red Hat, Inc., Raleigh, North Carolina</it> - </abstract> - - <!-- Table of contents --> - <toc> - -<!-- Begin the document --> -<sect>Introduction - -<sect1>The Distributed Multihead X Server - -<p>Current Open Source multihead solutions are limited to a single -physical machine. A single X server controls multiple display devices, -which can be arranged as independent heads or unified into a single -desktop (with Xinerama). These solutions are limited to the number of -physical devices that can co-exist in a single machine (e.g., due to the -number of AGP/PCI slots available for graphics cards). Thus, large -tiled displays are not currently possible. The work described in this -paper will eliminate the requirement that the display devices reside in -the same physical machine. This will be accomplished by developing a -front-end proxy X server that will control multiple back-end X servers -that make up the large display. - -<p>The overall structure of the distributed multihead X (DMX) project is -as follows: A single front-end X server will act as a proxy to a set of -back-end X servers, which handle all of the visible rendering. X -clients will connect to the front-end server just as they normally would -to a regular X server. The front-end server will present an abstracted -view to the client of a single large display. This will ensure that all -standard X clients will continue to operate without modification -(limited, as always, by the visuals and extensions provided by the X -server). Clients that are DMX-aware will be able to use an extension to -obtain information about the back-end servers (e.g., for placement of -pop-up windows, window alignments by the window manager, etc.). - -<p>The architecture of the DMX server is divided into two main sections: -input (e.g., mouse and keyboard events) and output (e.g., rendering and -windowing requests). Each of these are describe briefly below, and the -rest of this design document will describe them in greater detail. - -<p>The DMX server can receive input from three general types of input -devices: "local" devices that are physically attached to the machine on -which DMX is running, "backend" devices that are physically attached to -one or more of the back-end X servers (and that generate events via the -X protocol stream from the backend), and "console" devices that can be -abstracted from any non-back-end X server. Backend and console devices -are treated differently because the pointer device on the back-end X -server also controls the location of the hardware X cursor. Full -support for XInput extension devices is provided. - -<p>Rendering requests will be accepted by the front-end server; however, -rendering to visible windows will be broken down as needed and sent to -the appropriate back-end server(s) via X11 library calls for actual -rendering. The basic framework will follow a Xnest-style approach. GC -state will be managed in the front-end server and sent to the -appropriate back-end server(s) as required. Pixmap rendering will (at -least initially) be handled by the front-end X server. Windowing -requests (e.g., ordering, mapping, moving, etc.) will handled in the -front-end server. If the request requires a visible change, the -windowing operation will be translated into requests for the appropriate -back-end server(s). Window state will be mirrored in the back-end -server(s) as needed. - -<sect1>Layout of Paper - -<p>The next section describes the general development plan that was -actually used for implementation. The final section discusses -outstanding issues at the conclusion of development. The first appendix -provides low-level technical detail that may be of interest to those -intimately familiar with the X server architecture. The final appendix -describes the four phases of development that were performed during the -first two years of development. - -<p>The final year of work was divided into 9 tasks that are not -described in specific sections of this document. The major tasks during -that time were the enhancement of the reconfiguration ability added in -Phase IV, addition of support for a dynamic number of back-end displays -(instead of a hard-coded limit), and the support for back-end display -and input removal and addition. This work is mentioned in this paper, -but is not covered in detail. - -<!-- ============================================================ --> -<sect>Development plan - -<p>This section describes the development plan from approximately June -2001 through July 2003. - -<sect1>Bootstrap code - -<p>To allow for rapid development of the DMX server by multiple -developers during the first development stage, the problem will be -broken down into three tasks: the overall DMX framework, back-end -rendering services and input device handling services. However, before -the work begins on these tasks, a simple framework that each developer -could use was implemented to bootstrap the development effort. This -framework renders to a single back-end server and provides dummy input -devices (i.e., the keyboard and mouse). The simple back-end rendering -service was implemented using the shadow framebuffer support currently -available in the XFree86 environment. - -<p>Using this bootstrapping framework, each developer has been able to -work on each of the tasks listed above independently as follows: the -framework will be extended to handle arbitrary back-end server -configurations; the back-end rendering services will be transitioned to -the more efficient Xnest-style implementation; and, an input device -framework to handle various input devices via the input extension will -be developed. - -<p>Status: The boot strap code is complete. <!-- August 2001 --> - - -<sect1>Input device handling - -<p>An X server (including the front-end X server) requires two core -input devices -- a keyboard and a pointer (mouse). These core devices -are handled and required by the core X11 protocol. Additional types of -input devices may be attached and utilized via the XInput extension. -These are usually referred to as ``XInput extension devices'', - -<p>There are some options as to how the front-end X server gets its core -input devices: - -<enum> - <item>Local Input. The physical input devices (e.g., keyboard and - mouse) can be attached directly to the front-end X server. In this - case, the keyboard and mouse on the machine running the front-end X - server will be used. The front-end will have drivers to read the - raw input from those devices and convert it into the required X - input events (e.g., key press/release, pointer button press/release, - pointer motion). The front-end keyboard driver will keep track of - keyboard properties such as key and modifier mappings, autorepeat - state, keyboard sound and led state. Similarly the front-end - pointer driver will keep track if pointer properties such as the - button mapping and movement acceleration parameters. With this - option, input is handled fully in the front-end X server, and the - back-end X servers are used in a display-only mode. This option was - implemented and works for a limited number of Linux-specific - devices. Adding additional local input devices for other - architectures is expected to be relatively simple. - - <p>The following options are available for implementing local input - devices: - - <enum> - <item>The XFree86 X server has modular input drivers that could - be adapted for this purpose. The mouse driver supports a wide - range of mouse types and interfaces, as well as a range of - Operating System platforms. The keyboard driver in XFree86 is - not currently as modular as the mouse driver, but could be made - so. The XFree86 X server also has a range of other input - drivers for extended input devices such as tablets and touch - screens. Unfortunately, the XFree86 drivers are generally - complex, often simultaneously providing support for multiple - devices across multiple architectures; and rely so heavily on - XFree86-specific helper-functions, that this option was not - pursued. - - - <item>The <tt/kdrive/ X server in XFree86 has built-in drivers that - support PS/2 mice and keyboard under Linux. The mouse driver - can indirectly handle other mouse types if the Linux utility - <tt/gpm/ is used as to translate the native mouse protocol into - PS/2 mouse format. These drivers could be adapted and built in - to the front-end X server if this range of hardware and OS - support is sufficient. While much simpler than the XFree86 - drivers, the <tt/kdrive/ drivers were not used for the DMX - implementation. - - <item>Reimplementation of keyboard and mouse drivers from - scratch for the DMX framework. Because keyboard and mouse - drivers are relatively trivial to implement, this pathway was - selected. Other drivers in the X source tree were referenced, - and significant contributions from other drivers are noted in - the DMX source code. - </enum> - - <item>Backend Input. The front-end can make use of the core input - devices attached to one or more of the back-end X servers. Core - input events from multiple back-ends are merged into a single input - event stream. This can work sanely when only a single set of input - devices is used at any given time. The keyboard and pointer state - will be handled in the front-end, with changes propagated to the - back-end servers as needed. This option was implemented and works - well. Because the core pointer on a back-end controls the hardware - mouse on that back-end, core pointers cannot be treated as XInput - extension devices. However, all back-end XInput extensions devices - can be mapped to either DMX core or DMX XInput extension devices. - - <item>Console Input. The front-end server could create a console - window that is displayed on an X server independent of the back-end - X servers. This console window could display things like the - physical screen layout, and the front-end could get its core input - events from events delivered to the console window. This option was - implemented and works well. To help the human navigate, window - outlines are also displayed in the console window. Further, console - windows can be used as either core or XInput extension devices. - - <item>Other options were initially explored, but they were all - partial subsets of the options listed above and, hence, are - irrelevant. - -</enum> - -<p>Although extended input devices are not specifically mentioned in the -Distributed X requirements, the options above were all implemented so -that XInput extension devices were supported. - -<p>The bootstrap code (Xdmx) had dummy input devices, and these are -still supported in the final version. These do the necessary -initialization to satisfy the X server's requirements for core pointer -and keyboard devices, but no input events are ever generated. - -<p>Status: The input code is complete. Because of the complexity of the -XFree86 input device drivers (and their heavy reliance on XFree86 -infrastructure), separate low-level device drivers were implemented for -Xdmx. The following kinds of drivers are supported (in general, the -devices can be treated arbitrarily as "core" input devices or as XInput -"extension" devices; and multiple instances of different kinds of -devices can be simultaneously available): - <enum> - <item> A "dummy" device drive that never generates events. - - <item> "Local" input is from the low-level hardware on which the - Xdmx binary is running. This is the only area where using the - XFree86 driver infrastructure would have been helpful, and then - only partially, since good support for generic USB devices does - not yet exist in XFree86 (in any case, XFree86 and kdrive driver - code was used where possible). Currently, the following local - devices are supported under Linux (porting to other operating - systems should be fairly straightforward): - <itemize> - <item>Linux keyboard - <item>Linux serial mouse (MS) - <item>Linux PS/2 mouse - <item>USB keyboard - <item>USB mouse - <item>USB generic device (e.g., joystick, gamepad, etc.) - </itemize> - - <item> "Backend" input is taken from one or more of the back-end - displays. In this case, events are taken from the back-end X - server and are converted to Xdmx events. Care must be taken so - that the sprite moves properly on the display from which input - is being taken. - - <item> "Console" input is taken from an X window that Xdmx - creates on the operator's display (i.e., on the machine running - the Xdmx binary). When the operator's mouse is inside the - console window, then those events are converted to Xdmx events. - Several special features are available: the console can display - outlines of windows that are on the Xdmx display (to facilitate - navigation), the cursor can be confined to the console, and a - "fine" mode can be activated to allow very precise cursor - positioning. - </enum> - - -<!-- May 2002; July 2003 --> - -<sect1>Output device handling - -<p>The output of the DMX system displays rendering and windowing -requests across multiple screens. The screens are typically arranged in -a grid such that together they represent a single large display. - -<p>The output section of the DMX code consists of two parts. The first -is in the front-end proxy X server (Xdmx), which accepts client -connections, manages the windows, and potentially renders primitives but -does not actually display any of the drawing primitives. The second -part is the back-end X server(s), which accept commands from the -front-end server and display the results on their screens. - -<sect2>Initialization - -<p>The DMX front-end must first initialize its screens by connecting to -each of the back-end X servers and collecting information about each of -these screens. However, the information collected from the back-end X -servers might be inconsistent. Handling these cases can be difficult -and/or inefficient. For example, a two screen system has one back-end X -server running at 16bpp while the second is running at 32bpp. -Converting rendering requests (e.g., XPutImage() or XGetImage() -requests) to the appropriate bit depth can be very time consuming. -Analyzing these cases to determine how or even if it is possible to -handle them is required. The current Xinerama code handles many of -these cases (e.g., in PanoramiXConsolidate()) and will be used as a -starting point. In general, the best solution is to use homogeneous X -servers and display devices. Using back-end servers with the same depth -is a requirement of the final DMX implementation. - -<p>Once this screen consolidation is finished, the relative position of -each back-end X server's screen in the unified screen is initialized. A -full-screen window is opened on each of the back-end X servers, and the -cursor on each screen is turned off. The final DMX implementation can -also make use of a partial-screen window, or multiple windows per -back-end screen. - -<sect2>Handling rendering requests - -<p>After initialization, X applications connect to the front-end server. -There are two possible implementations of how rendering and windowing -requests are handled in the DMX system: - -<enum> - <item>A shadow framebuffer is used in the front-end server as the - render target. In this option, all protocol requests are completely - handled in the front-end server. All state and resources are - maintained in the front-end including a shadow copy of the entire - framebuffer. The framebuffers attached to the back-end servers are - updated by XPutImage() calls with data taken directly from the - shadow framebuffer. - - <p>This solution suffers from two main problems. First, it does not - take advantage of any accelerated hardware available in the system. - Second, the size of the XPutImage() calls can be quite large and - thus will be limited by the bandwidth available. - - <p>The initial DMX implementation used a shadow framebuffer by - default. - - <item>Rendering requests are sent to each back-end server for - handling (as is done in the Xnest server described above). In this - option, certain protocol requests are handled in the front-end - server and certain requests are repackaged and then sent to the - back-end servers. The framebuffer is distributed across the - multiple back-end servers. Rendering to the framebuffer is handled - on each back-end and can take advantage of any acceleration - available on the back-end servers' graphics display device. State - is maintained both in the front and back-end servers. - - <p>This solution suffers from two main drawbacks. First, protocol - requests are sent to all back-end servers -- even those that will - completely clip the rendering primitive -- which wastes bandwidth - and processing time. Second, state is maintained both in the front- - and back-end servers. These drawbacks are not as severe as in - option 1 (above) and can either be overcome through optimizations or - are acceptable. Therefore, this option will be used in the final - implementation. - - <p>The final DMX implementation defaults to this mechanism, but also - supports the shadow framebuffer mechanism. Several optimizations - were implemented to eliminate the drawbacks of the default - mechanism. These optimizations are described the section below and - in Phase II of the Development Results (see appendix). - -</enum> - -<p>Status: Both the shadow framebuffer and Xnest-style code is complete. -<!-- May 2002 --> - - -<sect1>Optimizing DMX - -<p>Initially, the Xnest-style solution's performance will be measured -and analyzed to determine where the performance bottlenecks exist. -There are four main areas that will be addressed. - -<p>First, to obtain reasonable interactivity with the first development -phase, XSync() was called after each protocol request. The XSync() -function flushes any pending protocol requests. It then waits for the -back-end to process the request and send a reply that the request has -completed. This happens with each back-end server and performance -greatly suffers. As a result of the way XSync() is called in the first -development phase, the batching that the X11 library performs is -effectively defeated. The XSync() call usage will be analyzed and -optimized by batching calls and performing them at regular intervals, -except where interactivity will suffer (e.g., on cursor movements). - -<p>Second, the initial Xnest-style solution described above sends the -repackaged protocol requests to all back-end servers regardless of -whether or not they would be completely clipped out. The requests that -are trivially rejected on the back-end server wastes the limited -bandwidth available. By tracking clipping changes in the DMX X server's -windowing code (e.g., by opening, closing, moving or resizing windows), -we can determine whether or not back-end windows are visible so that -trivial tests in the front-end server's GC ops drawing functions can -eliminate these unnecessary protocol requests. - -<p>Third, each protocol request will be analyzed to determine if it is -possible to break the request into smaller pieces at display boundaries. -The initial ones to be analyzed are put and get image requests since -they will require the greatest bandwidth to transmit data between the -front and back-end servers. Other protocol requests will be analyzed -and those that will benefit from breaking them into smaller requests -will be implemented. - -<p>Fourth, an extension is being considered that will allow font glyphs to -be transferred from the front-end DMX X server to each back-end server. -This extension will permit the front-end to handle all font requests and -eliminate the requirement that all back-end X servers share the exact -same fonts as the front-end server. We are investigating the -feasibility of this extension during this development phase. - -<p>Other potential optimizations will be determined from the performance -analysis. - -<p>Please note that in our initial design, we proposed optimizing BLT -operations (e.g., XCopyArea() and window moves) by developing an -extension that would allow individual back-end servers to directly copy -pixel data to other back-end servers. This potential optimization was -in response to the simple image movement implementation that required -potentially many calls to GetImage() and PutImage(). However, the -current Xinerama implementation handles these BLT operations -differently. Instead of copying data to and from screens, they generate -expose events -- just as happens in the case when a window is moved from -off a screen to on screen. This approach saves the limited bandwidth -available between front and back-end servers and is being standardized -with Xinerama. It also eliminates the potential setup problems and -security issues resulting from having each back-end server open -connections to all other back-end servers. Therefore, we suggest -accepting Xinerama's expose event solution. - -<p>Also note that the approach proposed in the second and third -optimizations might cause backing store algorithms in the back-end to be -defeated, so a DMX X server configuration flag will be added to disable -these optimizations. - -<p>Status: The optimizations proposed above are complete. It was -determined that the using the xfs font server was sufficient and -creating a new mechanism to pass glyphs was redundant; therefore, the -fourth optimization proposed above was not included in DMX. -<!-- September 2002 --> - - -<sect1>DMX X extension support - -<p>The DMX X server keeps track of all the windowing information on the -back-end X servers, but does not currently export this information to -any client applications. An extension will be developed to pass the -screen information and back-end window IDs to DMX-aware clients. These -clients can then use this information to directly connect to and render -to the back-end windows. Bypassing the DMX X server allows DMX-aware -clients to break up complex rendering requests on their own and send -them directly to the windows on the back-end server's screens. An -example of a client that can make effective use of this extension is -Chromium. - -<p>Status: The extension, as implemented, is fully documented in -"Client-to-Server DMX Extension to the X Protocol". Future changes -might be required based on feedback and other proposed enhancements to -DMX. Currently, the following facilities are supported: -<enum> - <item> - Screen information (clipping rectangle for each screen relative - to the virtual screen) - <item> - Window information (window IDs and clipping information for each - back-end window that corresponds to each DMX window) - <item> - Input device information (mappings from DMX device IDs to - back-end device IDs) - <item> - Force window creation (so that a client can override the - server-side lazy window creation optimization) - <item> - Reconfiguration (so that a client can request that a screen - position be changed) - <item> - Addition and removal of back-end servers and back-end and - console inputs. -</enum> -<!-- September 2002; July 2003 --> - - -<sect1>Common X extension support - -<p>The XInput, XKeyboard and Shape extensions are commonly used -extensions to the base X11 protocol. XInput allows multiple and -non-standard input devices to be accessed simultaneously. These input -devices can be connected to either the front-end or back-end servers. -XKeyboard allows much better keyboard mappings control. Shape adds -support for arbitrarily shaped windows and is used by various window -managers. Nearly all potential back-end X servers make these extensions -available, and support for each one will be added to the DMX system. - -<p>In addition to the extensions listed above, support for the X -Rendering extension (Render) is being developed. Render adds digital -image composition to the rendering model used by the X Window System. -While this extension is still under development by Keith Packard of HP, -support for the current version will be added to the DMX system. - -<p>Support for the XTest extension was added during the first -development phase. - -<!-- WARNING: this list is duplicated in the Phase IV discussion --> -<p>Status: The following extensions are supported and are discussed in -more detail in Phase IV of the Development Results (see appendix): - BIG-REQUESTS, - DEC-XTRAP, - DMX, - DPMS, - Extended-Visual-Information, - GLX, - LBX, - RECORD, - RENDER, - SECURITY, - SHAPE, - SYNC, - X-Resource, - XC-APPGROUP, - XC-MISC, - XFree86-Bigfont, - XINERAMA, - XInputExtension, - XKEYBOARD, and - XTEST. -<!-- November 2002; updated February 2003, July 2003 --> - -<sect1>OpenGL support - -<p>OpenGL support using the Mesa code base exists in XFree86 release 4 -and later. Currently, the direct rendering infrastructure (DRI) -provides accelerated OpenGL support for local clients and unaccelerated -OpenGL support (i.e., software rendering) is provided for non-local -clients. - -<p>The single head OpenGL support in XFree86 4.x will be extended to use -the DMX system. When the front and back-end servers are on the same -physical hardware, it is possible to use the DRI to directly render to -the back-end servers. First, the existing DRI will be extended to -support multiple display heads, and then to support the DMX system. -OpenGL rendering requests will be direct rendering to each back-end X -server. The DRI will request the screen layout (either from the -existing Xinerama extension or a DMX-specific extension). Support for -synchronized swap buffers will also be added (on hardware that supports -it). Note that a single front-end server with a single back-end server -on the same physical machine can emulate accelerated indirect rendering. - -<p>When the front and back-end servers are on different physical -hardware or are using non-XFree86 4.x X servers, a mechanism to render -primitives across the back-end servers will be provided. There are -several options as to how this can be implemented. - -<enum> - <item>The existing OpenGL support in each back-end server can be - used by repackaging rendering primitives and sending them to each - back-end server. This option is similar to the unoptimized - Xnest-style approach mentioned above. Optimization of this solution - is beyond the scope of this project and is better suited to other - distributed rendering systems. - - <item>Rendering to a pixmap in the front-end server using the - current XFree86 4.x code, and then displaying to the back-ends via - calls to XPutImage() is another option. This option is similar to - the shadow frame buffer approach mentioned above. It is slower and - bandwidth intensive, but has the advantage that the back-end servers - are not required to have OpenGL support. -</enum> - -<p>These, and other, options will be investigated in this phase of the -work. - -<p>Work by others have made Chromium DMX-aware. Chromium will use the -DMX X protocol extension to obtain information about the back-end -servers and will render directly to those servers, bypassing DMX. - -<p>Status: OpenGL support by the glxProxy extension was implemented by -SGI and has been integrated into the DMX code base. -<!-- May 2003--> - - -<!-- ============================================================ --> -<sect>Current issues - -<p>In this sections the current issues are outlined that require further -investigation. - -<sect1>Fonts - -<p>The font path and glyphs need to be the same for the front-end and -each of the back-end servers. Font glyphs could be sent to the back-end -servers as necessary but this would consume a significant amount of -available bandwidth during font rendering for clients that use many -different fonts (e.g., Netscape). Initially, the font server (xfs) will -be used to provide the fonts to both the front-end and back-end servers. -Other possibilities will be investigated during development. - -<sect1>Zero width rendering primitives - -<p>To allow pixmap and on-screen rendering to be pixel perfect, all -back-end servers must render zero width primitives exactly the same as -the front-end renders the primitives to pixmaps. For those back-end -servers that do not exactly match, zero width primitives will be -automatically converted to one width primitives. This can be handled in -the front-end server via the GC state. - -<sect1>Output scaling - -<p>With very large tiled displays, it might be difficult to read the -information on the standard X desktop. In particular, the cursor can be -easily lost and fonts could be difficult to read. Automatic primitive -scaling might prove to be very useful. We will investigate the -possibility of scaling the cursor and providing a set of alternate -pre-scaled fonts to replace the standard fonts that many applications -use (e.g., fixed). Other options for automatic scaling will also be -investigated. - -<sect1>Per-screen colormaps - -<p>Each screen's default colormap in the set of back-end X servers -should be able to be adjusted via a configuration utility. This support -is would allow the back-end screens to be calibrated via custom gamma -tables. On 24-bit systems that support a DirectColor visual, this type -of correction can be accommodated. One possible implementation would be -to advertise to X client of the DMX server a TrueColor visual while -using DirectColor visuals on the back-end servers to implement this type -of color correction. Other options will be investigated. - -<!-- ============================================================ --> -<appendix> - -<sect>Background - -<p>This section describes the existing Open Source architectures that -can be used to handle multiple screens and upon which this development -project is based. This section was written before the implementation -was finished, and may not reflect actual details of the implementation. -It is left for historical interest only. - -<sect1>Core input device handling - -<p>The following is a description of how core input devices are handled -by an X server. - -<sect2>InitInput() - -<p>InitInput() is a DDX function that is called at the start of each -server generation from the X server's main() function. Its purpose is -to determine what input devices are connected to the X server, register -them with the DIX and MI layers, and initialize the input event queue. -InitInput() does not have a return value, but the X server will abort if -either a core keyboard device or a core pointer device are not -registered. Extended input (XInput) devices can also be registered in -InitInput(). - -<p>InitInput() usually has implementation specific code to determine -which input devices are available. For each input device it will be -using, it calls AddInputDevice(): - -<descrip> -<tag/AddInputDevice()/ This DIX function allocates the device structure, -registers a callback function (which handles device init, close, on and -off), and returns the input handle, which can be treated as opaque. It -is called once for each input device. -</descrip> - -<p>Once input handles for core keyboard and core pointer devices have -been obtained from AddInputDevice(), they are registered as core devices -by calling RegisterPointerDevice() and RegisterKeyboardDevice(). Each -of these should be called once. If both core devices are not -registered, then the X server will exit with a fatal error when it -attempts to start the input devices in InitAndStartDevices(), which is -called directly after InitInput() (see below). - -<descrip> -<tag/Register{Pointer,Keyboard}Device()/ These DIX functions take a -handle returned from AddInputDevice() and initialize the core input -device fields in inputInfo, and initialize the input processing and grab -functions for each core input device. -</descrip> - -<p>The core pointer device is then registered with the miPointer code -(which does the high level cursor handling). While this registration -is not necessary for correct miPointer operation in the current XFree86 -code, it is still done mostly for compatibility reasons. - -<descrip> -<tag/miRegisterPointerDevice()/ This MI function registers the core -pointer's input handle with with the miPointer code. -</descrip> - -<p>The final part of InitInput() is the initialization of the input -event queue handling. In most cases, the event queue handling provided -in the MI layer is used. The primary XFree86 X server uses its own -event queue handling to support some special cases related to the XInput -extension and the XFree86-specific DGA extension. For our purposes, the -MI event queue handling should be suitable. It is initialized by -calling mieqInit(): - -<descrip> -<tag/mieqInit()/ This MI function initializes the MI event queue for the -core devices, and is passed the public component of the input handles -for the two core devices. -</descrip> - -<p>If a wakeup handler is required to deliver synchronous input -events, it can be registered here by calling the DIX function -RegisterBlockAndWakeupHandlers(). (See the devReadInput() description -below.) - -<sect2>InitAndStartDevices() - -<p>InitAndStartDevices() is a DIX function that is called immediately -after InitInput() from the X server's main() function. Its purpose is -to initialize each input device that was registered with -AddInputDevice(), enable each input device that was successfully -initialized, and create the list of enabled input devices. Once each -registered device is processed in this way, the list of enabled input -devices is checked to make sure that both a core keyboard device and -core pointer device were registered and successfully enabled. If not, -InitAndStartDevices() returns failure, and results in the the X server -exiting with a fatal error. - -<p>Each registered device is initialized by calling its callback -(dev->deviceProc) with the DEVICE_INIT argument: - -<descrip> -<tag/(*dev->deviceProc)(dev, DEVICE_INIT)/ This function initializes the -device structs with core information relevant to the device. - -<p>For pointer devices, this means specifying the number of buttons, -default button mapping, the function used to get motion events (usually -miPointerGetMotionEvents()), the function used to change/control the -core pointer motion parameters (acceleration and threshold), and the -motion buffer size. - -<p>For keyboard devices, this means specifying the keycode range, -default keycode to keysym mapping, default modifier mapping, and the -functions used to sound the keyboard bell and modify/control the -keyboard parameters (LEDs, bell pitch and duration, key click, which -keys are auto-repeating, etc). -</descrip> - -<p>Each initialized device is enabled by calling EnableDevice(): - -<descrip> -<tag/EnableDevice()/ EnableDevice() calls the device callback with -DEVICE_ON: - <descrip> - <tag/(*dev->deviceProc)(dev, DEVICE_ON)/ This typically opens and - initializes the relevant physical device, and when appropriate, - registers the device's file descriptor (or equivalent) as a valid - input source. - </descrip> - - <p>EnableDevice() then adds the device handle to the X server's - global list of enabled devices. -</descrip> - -<p>InitAndStartDevices() then verifies that a valid core keyboard and -pointer has been initialized and enabled. It returns failure if either -are missing. - -<sect2>devReadInput() - -<p>Each device will have some function that gets called to read its -physical input. These may be called in a number of different ways. In -the case of synchronous I/O, they will be called from a DDX -wakeup-handler that gets called after the server detects that new input is -available. In the case of asynchronous I/O, they will be called from a -(SIGIO) signal handler triggered when new input is available. This -function should do at least two things: make sure that input events get -enqueued, and make sure that the cursor gets moved for motion events -(except if these are handled later by the driver's own event queue -processing function, which cannot be done when using the MI event queue -handling). - -<p>Events are queued by calling mieqEnqueue(): - -<descrip> -<tag/mieqEnqueue()/ This MI function is used to add input events to the -event queue. It is simply passed the event to be queued. -</descrip> - -<p>The cursor position should be updated when motion events are -enqueued, by calling either miPointerAbsoluteCursor() or -miPointerDeltaCursor(): - -<descrip> -<tag/miPointerAbsoluteCursor()/ This MI function is used to move the -cursor to the absolute coordinates provided. -<tag/miPointerDeltaCursor()/ This MI function is used to move the cursor -relative to its current position. -</descrip> - -<sect2>ProcessInputEvents() - -<p>ProcessInputEvents() is a DDX function that is called from the X -server's main dispatch loop when new events are available in the input -event queue. It typically processes the enqueued events, and updates -the cursor/pointer position. It may also do other DDX-specific event -processing. - -<p>Enqueued events are processed by mieqProcessInputEvents() and passed -to the DIX layer for transmission to clients: - -<descrip> -<tag/mieqProcessInputEvents()/ This function processes each event in the -event queue, and passes it to the device's input processing function. -The DIX layer provides default functions to do this processing, and they -handle the task of getting the events passed back to the relevant -clients. -<tag/miPointerUpdate()/ This function resynchronized the cursor position -with the new pointer position. It also takes care of moving the cursor -between screens when needed in multi-head configurations. -</descrip> - - -<sect2>DisableDevice() - -<p>DisableDevice is a DIX function that removes an input device from the -list of enabled devices. The result of this is that the device no -longer generates input events. The device's data structures are kept in -place, and disabling a device like this can be reversed by calling -EnableDevice(). DisableDevice() may be called from the DDX when it is -desirable to do so (e.g., the XFree86 server does this when VT -switching). Except for special cases, this is not normally called for -core input devices. - -<p>DisableDevice() calls the device's callback function with -<tt/DEVICE_OFF/: - -<descrip> -<tag/(*dev->deviceProc)(dev, DEVICE_OFF)/ This typically closes the -relevant physical device, and when appropriate, unregisters the device's -file descriptor (or equivalent) as a valid input source. -</descrip> - -<p>DisableDevice() then removes the device handle from the X server's -global list of enabled devices. - - -<sect2>CloseDevice() - -<p>CloseDevice is a DIX function that removes an input device from the -list of available devices. It disables input from the device and frees -all data structures associated with the device. This function is -usually called from CloseDownDevices(), which is called from main() at -the end of each server generation to close all input devices. - -<p>CloseDevice() calls the device's callback function with -<tt/DEVICE_CLOSE/: - -<descrip> -<tag/(*dev->deviceProc)(dev, DEVICE_CLOSE)/ This typically closes the -relevant physical device, and when appropriate, unregisters the device's -file descriptor (or equivalent) as a valid input source. If any device -specific data structures were allocated when the device was initialized, -they are freed here. -</descrip> - -<p>CloseDevice() then frees the data structures that were allocated -for the device when it was registered/initialized. - - -<sect2>LegalModifier() -<!-- dmx/dmxinput.c - currently returns TRUE --> -<p>LegalModifier() is a required DDX function that can be used to -restrict which keys may be modifier keys. This seems to be present for -historical reasons, so this function should simply return TRUE -unconditionally. - - -<sect1>Output handling - -<p>The following sections describe the main functions required to -initialize, use and close the output device(s) for each screen in the X -server. - -<sect2>InitOutput() - -<p>This DDX function is called near the start of each server generation -from the X server's main() function. InitOutput()'s main purpose is to -initialize each screen and fill in the global screenInfo structure for -each screen. It is passed three arguments: a pointer to the screenInfo -struct, which it is to initialize, and argc and argv from main(), which -can be used to determine additional configuration information. - -<p>The primary tasks for this function are outlined below: - -<enum> - <item><bf/Parse configuration info:/ The first task of InitOutput() - is to parses any configuration information from the configuration - file. In addition to the XF86Config file, other configuration - information can be taken from the command line. The command line - options can be gathered either in InitOutput() or earlier in the - ddxProcessArgument() function, which is called by - ProcessCommandLine(). The configuration information determines the - characteristics of the screen(s). For example, in the XFree86 X - server, the XF86Config file specifies the monitor information, the - screen resolution, the graphics devices and slots in which they are - located, and, for Xinerama, the screens' layout. - - <item><bf/Initialize screen info:/ The next task is to initialize - the screen-dependent internal data structures. For example, part of - what the XFree86 X server does is to allocate its screen and pixmap - private indices, probe for graphics devices, compare the probed - devices to the ones listed in the XF86Config file, and add the ones that - match to the internal xf86Screens[] structure. - - <item><bf/Set pixmap formats:/ The next task is to initialize the - screenInfo's image byte order, bitmap bit order and bitmap scanline - unit/pad. The screenInfo's pixmap format's depth, bits per pixel - and scanline padding is also initialized at this stage. - - <item><bf/Unify screen info:/ An optional task that might be done at - this stage is to compare all of the information from the various - screens and determines if they are compatible (i.e., if the set of - screens can be unified into a single desktop). This task has - potential to be useful to the DMX front-end server, if Xinerama's - PanoramiXConsolidate() function is not sufficient. -</enum> - -<p>Once these tasks are complete, the valid screens are known and each -of these screens can be initialized by calling AddScreen(). - -<sect2>AddScreen() - -<p>This DIX function is called from InitOutput(), in the DDX layer, to -add each new screen to the screenInfo structure. The DDX screen -initialization function and command line arguments (i.e., argc and argv) -are passed to it as arguments. - -<p>This function first allocates a new Screen structure and any privates -that are required. It then initializes some of the fields in the Screen -struct and sets up the pixmap padding information. Finally, it calls -the DDX screen initialization function ScreenInit(), which is described -below. It returns the number of the screen that were just added, or -1 -if there is insufficient memory to add the screen or if the DDX screen -initialization fails. - -<sect2>ScreenInit() - -<p>This DDX function initializes the rest of the Screen structure with -either generic or screen-specific functions (as necessary). It also -fills in various screen attributes (e.g., width and height in -millimeters, black and white pixel values). - -<p>The screen init function usually calls several functions to perform -certain screen initialization functions. They are described below: - -<descrip> -<tag/{mi,*fb}ScreenInit()/ The DDX layer's ScreenInit() function usually -calls another layer's ScreenInit() function (e.g., miScreenInit() or -fbScreenInit()) to initialize the fallbacks that the DDX driver does not -specifically handle. - -<p>After calling another layer's ScreenInit() function, any -screen-specific functions either wrap or replace the other layer's -function pointers. If a function is to be wrapped, each of the old -function pointers from the other layer are stored in a screen private -area. Common functions to wrap are CloseScreen() and SaveScreen(). - -<tag/miInitializeBackingStore()/ This MI function initializes the -screen's backing storage functions, which are used to save areas of -windows that are currently covered by other windows. - -<tag/miDCInitialize()/ This MI function initializes the MI cursor -display structures and function pointers. If a hardware cursor is used, -the DDX layer's ScreenInit() function will wrap additional screen and -the MI cursor display function pointers. -</descrip> - -<p>Another common task for ScreenInit() function is to initialize the -output device state. For example, in the XFree86 X server, the -ScreenInit() function saves the original state of the video card and -then initializes the video mode of the graphics device. - -<sect2>CloseScreen() - -<p>This function restores any wrapped screen functions (and in -particular the wrapped CloseScreen() function) and restores the state of -the output device to its original state. It should also free any -private data it created during the screen initialization. - -<sect2>GC operations - -<p>When the X server is requested to render drawing primitives, it does -so by calling drawing functions through the graphics context's operation -function pointer table (i.e., the GCOps functions). These functions -render the basic graphics operations such as drawing rectangles, lines, -text or copying pixmaps. Default routines are provided either by the MI -layer, which draws indirectly through a simple span interface, or by the -framebuffer layers (e.g., CFB, MFB, FB), which draw directly to a -linearly mapped frame buffer. - -<p>To take advantage of special hardware on the graphics device, -specific GCOps functions can be replaced by device specific code. -However, many times the graphics devices can handle only a subset of the -possible states of the GC, so during graphics context validation, -appropriate routines are selected based on the state and capabilities of -the hardware. For example, some graphics hardware can accelerate single -pixel width lines with certain dash patterns. Thus, for dash patterns -that are not supported by hardware or for width 2 or greater lines, the -default routine is chosen during GC validation. - -<p>Note that some pointers to functions that draw to the screen are -stored in the Screen structure. They include GetImage(), GetSpans(), -CopyWindow() and RestoreAreas(). - -<sect2>Xnest - -<p>The Xnest X server is a special proxy X server that relays the X -protocol requests that it receives to a ``real'' X server that then -processes the requests and displays the results, if applicable. To the X -applications, Xnest appears as if it is a regular X server. However, -Xnest is both server to the X application and client of the real X -server, which will actually handle the requests. - -<p>The Xnest server implements all of the standard input and output -initialization steps outlined above. - -<descrip> -<tag/InitOutput()/ Xnest takes its configuration information from -command line arguments via ddxProcessArguments(). This information -includes the real X server display to connect to, its default visual -class, the screen depth, the Xnest window's geometry, etc. Xnest then -connects to the real X server and gathers visual, colormap, depth and -pixmap information about that server's display, creates a window on that -server, which will be used as the root window for Xnest. - -<p>Next, Xnest initializes its internal data structures and uses the -data from the real X server's pixmaps to initialize its own pixmap -formats. Finally, it calls AddScreen(xnestOpenScreen, argc, argv) to -initialize each of its screens. - -<tag/ScreenInit()/ Xnest's ScreenInit() function is called -xnestOpenScreen(). This function initializes its screen's depth and -visual information, and then calls miScreenInit() to set up the default -screen functions. It then calls miInitializeBackingStore() and -miDCInitialize() to initialize backing store and the software cursor. -Finally, it replaces many of the screen functions with its own -functions that repackage and send the requests to the real X server to -which Xnest is attached. - -<tag/CloseScreen()/ This function frees its internal data structure -allocations. Since it replaces instead of wrapping screen functions, -there are no function pointers to unwrap. This can potentially lead to -problems during server regeneration. - -<tag/GC operations/ The GC operations in Xnest are very simple since -they leave all of the drawing to the real X server to which Xnest is -attached. Each of the GCOps takes the request and sends it to the -real X server using standard Xlib calls. For example, the X -application issues a XDrawLines() call. This function turns into a -protocol request to Xnest, which calls the xnestPolylines() function -through Xnest's GCOps function pointer table. The xnestPolylines() -function is only a single line, which calls XDrawLines() using the same -arguments that were passed into it. Other GCOps functions are very -similar. Two exceptions to the simple GCOps functions described above -are the image functions and the BLT operations. - -<p>The image functions, GetImage() and PutImage(), must use a temporary -image to hold the image to be put of the image that was just grabbed -from the screen while it is in transit to the real X server or the -client. When the image has been transmitted, the temporary image is -destroyed. - -<p>The BLT operations, CopyArea() and CopyPlane(), handle not only the -copy function, which is the same as the simple cases described above, -but also the graphics exposures that result when the GC's graphics -exposure bit is set to True. Graphics exposures are handled in a helper -function, xnestBitBlitHelper(). This function collects the exposure -events from the real X server and, if any resulting in regions being -exposed, then those regions are passed back to the MI layer so that it -can generate exposure events for the X application. -</descrip> - -<p>The Xnest server takes its input from the X server to which it is -connected. When the mouse is in the Xnest server's window, keyboard and -mouse events are received by the Xnest server, repackaged and sent back -to any client that requests those events. - -<sect2>Shadow framebuffer - -<p>The most common type of framebuffer is a linear array memory that -maps to the video memory on the graphics device. However, accessing -that video memory over an I/O bus (e.g., ISA or PCI) can be slow. The -shadow framebuffer layer allows the developer to keep the entire -framebuffer in main memory and copy it back to video memory at regular -intervals. It also has been extended to handle planar video memory and -rotated framebuffers. - -<p>There are two main entry points to the shadow framebuffer code: - -<descrip> -<tag/shadowAlloc(width, height, bpp)/ This function allocates the in -memory copy of the framebuffer of size width*height*bpp. It returns a -pointer to that memory, which will be used by the framebuffer -ScreenInit() code during the screen's initialization. - -<tag/shadowInit(pScreen, updateProc, windowProc)/ This function -initializes the shadow framebuffer layer. It wraps several screen -drawing functions, and registers a block handler that will update the -screen. The updateProc is a function that will copy the damaged regions -to the screen, and the windowProc is a function that is used when the -entire linear video memory range cannot be accessed simultaneously so -that only a window into that memory is available (e.g., when using the -VGA aperture). -</descrip> - -<p>The shadow framebuffer code keeps track of the damaged area of each -screen by calculating the bounding box of all drawing operations that -have occurred since the last screen update. Then, when the block handler -is next called, only the damaged portion of the screen is updated. - -<p>Note that since the shadow framebuffer is kept in main memory, all -drawing operations are performed by the CPU and, thus, no accelerated -hardware drawing operations are possible. - - -<sect1>Xinerama - -<p>Xinerama is an X extension that allows multiple physical screens -controlled by a single X server to appear as a single screen. Although -the extension allows clients to find the physical screen layout via -extension requests, it is completely transparent to clients at the core -X11 protocol level. The original public implementation of Xinerama came -from Digital/Compaq. XFree86 rewrote it, filling in some missing pieces -and improving both X11 core protocol compliance and performance. The -Xinerama extension will be passing through X.Org's standardization -process in the near future, and the sample implementation will be based -on this rewritten version. - -<p>The current implementation of Xinerama is based primarily in the DIX -(device independent) and MI (machine independent) layers of the X -server. With few exceptions the DDX layers do not need any changes to -support Xinerama. X server extensions often do need modifications to -provide full Xinerama functionality. - -<p>The following is a code-level description of how Xinerama functions. - -<p>Note: Because the Xinerama extension was originally called the -PanoramiX extension, many of the Xinerama functions still have the -PanoramiX prefix. - -<descrip> - <tag/PanoramiXExtensionInit()/ PanoramiXExtensionInit() is a - device-independent extension function that is called at the start of - each server generation from InitExtensions(), which is called from - the X server's main() function after all output devices have been - initialized, but before any input devices have been initialized. - - <p>PanoramiXNumScreens is set to the number of physical screens. If - only one physical screen is present, the extension is disabled, and - PanoramiXExtensionInit() returns without doing anything else. - - <p>The Xinerama extension is registered by calling AddExtension(). - - <p>A local per-screen array of data structures - (panoramiXdataPtr[]) - is allocated for each physical screen, and GC and Screen private - indexes are allocated, and both GC and Screen private areas are - allocated for each physical screen. These hold Xinerama-specific - per-GC and per-Screen data. Each screen's CreateGC and CloseScreen - functions are wrapped by XineramaCreateGC() and - XineramaCloseScreen() respectively. Some new resource classes are - created for Xinerama drawables and GCs, and resource types for - Xinerama windows, pixmaps and colormaps. - - <p>A region (XineramaScreenRegions[i]) is initialized for each - physical screen, and single region (PanoramiXScreenRegion) is - initialized to be the union of the screen regions. The - panoramiXdataPtr[] array is also initialized with the size and - origin of each screen. The relative positioning information for the - physical screens is taken from the array - dixScreenOrigins[], which - the DDX layer must initialize in InitOutput(). The bounds of the - combined screen is also calculated (PanoramiXPixWidth and - PanoramiXPixHeight). - - <p>The DIX layer has a list of function pointers - (ProcVector[]) that - holds the entry points for the functions that process core protocol - requests. The requests that Xinerama must intercept and break up - into physical screen-specific requests are wrapped. The original - set is copied to SavedProcVector[]. The types of requests - intercepted are Window requests, GC requests, colormap requests, - drawing requests, and some geometry-related requests. This wrapping - allows the bulk of the protocol request processing to be handled - transparently to the DIX layer. Some operations cannot be dealt with - in this way and are handled with Xinerama-specific code within the - DIX layer. - - <tag/PanoramiXConsolidate()/ PanoramiXConsolidate() is a - device-independent extension function that is called directly from - the X server's main() function after extensions and input/output - devices have been initialized, and before the root windows are - defined and initialized. - - <p>This function finds the set of depths (PanoramiXDepths[]) and - visuals (PanoramiXVisuals[]) - common to all of the physical screens. - PanoramiXNumDepths is set to the number of common depths, and - PanoramiXNumVisuals is set to the number of common visuals. - Resources are created for the single root window and the default - colormap. Each of these resources has per-physical screen entries. - - <tag/PanoramiXCreateConnectionBlock()/ PanoramiXConsolidate() is a - device-independent extension function that is called directly from - the X server's main() function after the per-physical screen root - windows are created. It is called instead of the standard DIX - CreateConnectionBlock() function. If this function returns FALSE, - the X server exits with a fatal error. This function will return - FALSE if no common depths were found in PanoramiXConsolidate(). - With no common depths, Xinerama mode is not possible. - - <p>The connection block holds the information that clients get when - they open a connection to the X server. It includes information - such as the supported pixmap formats, number of screens and the - sizes, depths, visuals, default colormap information, etc, for each - of the screens (much of information that <tt/xdpyinfo/ shows). The - connection block is initialized with the combined single screen - values that were calculated in the above two functions. - - <p>The Xinerama extension allows the registration of connection - block callback functions. The purpose of these is to allow other - extensions to do processing at this point. These callbacks can be - registered by calling XineramaRegisterConnectionBlockCallback() from - the other extension's ExtensionInit() function. Each registered - connection block callback is called at the end of - PanoramiXCreateConnectionBlock(). -</descrip> - -<sect2>Xinerama-specific changes to the DIX code - -<p>There are a few types of Xinerama-specific changes within the DIX -code. The main ones are described here. - -<p>Functions that deal with colormap or GC -related operations outside of -the intercepted protocol requests have a test added to only do the -processing for screen numbers > 0. This is because they are handled for -the single Xinerama screen and the processing is done once for screen 0. - -<p>The handling of motion events does some coordinate translation between -the physical screen's origin and screen zero's origin. Also, motion -events must be reported relative to the composite screen origin rather -than the physical screen origins. - -<p>There is some special handling for cursor, window and event processing -that cannot (either not at all or not conveniently) be done via the -intercepted protocol requests. A particular case is the handling of -pointers moving between physical screens. - -<sect2>Xinerama-specific changes to the MI code - -<p>The only Xinerama-specific change to the MI code is in miSendExposures() -to handle the coordinate (and window ID) translation for expose events. - -<sect2>Intercepted DIX core requests - -<p>Xinerama breaks up drawing requests for dispatch to each physical -screen. It also breaks up windows into pieces for each physical screen. -GCs are translated into per-screen GCs. Colormaps are replicated on -each physical screen. The functions handling the intercepted requests -take care of breaking the requests and repackaging them so that they can -be passed to the standard request handling functions for each screen in -turn. In addition, and to aid the repackaging, the information from -many of the intercepted requests is used to keep up to date the -necessary state information for the single composite screen. Requests -(usually those with replies) that can be satisfied completely from this -stored state information do not call the standard request handling -functions. - -<!-- ============================================================ --> - -<sect>Development Results - -<p>In this section the results of each phase of development are -discussed. This development took place between approximately June 2001 -and July 2003. - -<sect1>Phase I - -<p>The initial development phase dealt with the basic implementation -including the bootstrap code, which used the shadow framebuffer, and the -unoptimized implementation, based on an Xnest-style implementation. - -<sect2>Scope - -<p>The goal of Phase I is to provide fundamental functionality that can -act as a foundation for ongoing work: -<enum> - <item>Develop the proxy X server - <itemize> - <item>The proxy X server will operate on the X11 protocol and - relay requests as necessary to correctly perform the request. - <item>Work will be based on the existing work for Xinerama and - Xnest. - <item>Input events and windowing operations are handled in the - proxy server and rendering requests are repackaged and sent to - each of the back-end servers for display. - <item>The multiple screen layout (including support for - overlapping screens) will be user configurable via a - configuration file or through the configuration tool. - </itemize> - <item>Develop graphical configuration tool - <itemize> - <item>There will be potentially a large number of X servers to - configure into a single display. The tool will allow the user - to specify which servers are involved in the configuration and - how they should be laid out. - </itemize> - <item>Pass the X Test Suite - <itemize> - <item>The X Test Suite covers the basic X11 operations. All - tests known to succeed must correctly operate in the distributed - X environment. - </itemize> -</enum> - -<p>For this phase, the back-end X servers are assumed to be unmodified X -servers that do not support any DMX-related protocol extensions; future -optimization pathways are considered, but are not implemented; and the -configuration tool is assumed to rely only on libraries in the X source -tree (e.g., Xt). - -<sect2>Results - -<p>The proxy X server, Xdmx, was developed to distribute X11 protocol -requests to the set of back-end X servers. It opens a window on each -back-end server, which represents the part of the front-end's root -window that is visible on that screen. It mirrors window, pixmap and -other state in each back-end server. Drawing requests are sent to -either windows or pixmaps on each back-end server. This code is based -on Xnest and uses the existing Xinerama extension. - -<p>Input events can be taken from (1) devices attached to the back-end -server, (2) core devices attached directly to the Xdmx server, or (3) -from a ``console'' window on another X server. Events for these devices -are gathered, processed and delivered to clients attached to the Xdmx -server. - -<p>An intuitive configuration format was developed to help the user -easily configure the multiple back-end X servers. It was defined (see -grammar in Xdmx man page) and a parser was implemented that is used by -the Xdmx server and by a standalone xdmxconfig utility. The parsing -support was implemented such that it can be easily factored out of the X -source tree for use with other tools (e.g., vdl). Support for -converting legacy vdl-format configuration files to the DMX format is -provided by the vdltodmx utility. - -<p>Originally, the configuration file was going to be a subsection of -XFree86's XF86Config file, but that was not possible since Xdmx is a -completely separate X server. Thus, a separate config file format was -developed. In addition, a graphical configuration -tool, xdmxconfig, was developed to allow the user to create and arrange -the screens in the configuration file. The <bf/-configfile/ and <bf/-config/ -command-line options can be used to start Xdmx using a configuration -file. - -<p>An extension that enables remote input testing is required for the X -Test Suite to function. During this phase, this extension (XTEST) was -implemented in the Xdmx server. The results from running the X Test -Suite are described in detail below. - -<sect2>X Test Suite - - <sect3> Introduction - <p> - The X Test Suite contains tests that verify Xlib functions - operate correctly. The test suite is designed to run on a - single X server; however, since X applications will not be - able to tell the difference between the DMX server and a - standard X server, the X Test Suite should also run on the - DMX server. - <p> - The Xdmx server was tested with the X Test Suite, and the - existing failures are noted in this section. To put these - results in perspective, we first discuss expected X Test - failures and how errors in underlying systems can impact - Xdmx test results. - - <sect3>Expected Failures for a Single Head - <p> - A correctly implemented X server with a single screen is - expected to fail certain X Test tests. The following - well-known errors occur because of rounding error in the X - server code: - <verb> -XDrawArc: Tests 42, 63, 66, 73 -XDrawArcs: Tests 45, 66, 69, 76 - </verb> - <p> - The following failures occur because of the high-level X - server implementation: - <verb> -XLoadQueryFont: Test 1 -XListFontsWithInfo: Tests 3, 4 -XQueryFont: Tests 1, 2 - </verb> - <p> - The following test fails when running the X server as root - under Linux because of the way directory modes are - interpreted: - <verb> -XWriteBitmapFile: Test 3 - </verb> - <p> - Depending on the video card used for the back-end, other - failures may also occur because of bugs in the low-level - driver implementation. Over time, failures of this kind - are usually fixed by XFree86, but will show up in Xdmx - testing until then. - - <sect3>Expected Failures for Xinerama - <p> - Xinerama fails several X Test Suite tests because of - design decisions made for the current implementation of - Xinerama. Over time, many of these errors will be - corrected by XFree86 and the group working on a new - Xinerama implementation. Therefore, Xdmx will also share - X Suite Test failures with Xinerama. - <p> - We may be able to fix or work-around some of these - failures at the Xdmx level, but this will require - additional exploration that was not part of Phase I. - <p> - Xinerama is constantly improving, and the list of - Xinerama-related failures depends on XFree86 version and - the underlying graphics hardware. We tested with a - variety of hardware, including nVidia, S3, ATI Radeon, - and Matrox G400 (in dual-head mode). The list below - includes only those failures that appear to be from the - Xinerama layer, and does not include failures listed in - the previous section, or failures that appear to be from - the low-level graphics driver itself: - <p> - These failures were noted with multiple Xinerama - configurations: - <verb> -XCopyPlane: Tests 13, 22, 31 (well-known Xinerama implementation issue) -XSetFontPath: Test 4 -XGetDefault: Test 5 -XMatchVisualInfo: Test 1 - </verb> - <p> - These failures were noted only when using one dual-head - video card with a 4.2.99.x XFree86 server: - <verb> -XListPixmapFormats: Test 1 -XDrawRectangles: Test 45 - </verb> - <p> - These failures were noted only when using two video cards - from different vendors with a 4.1.99.x XFree86 server: - <verb> -XChangeWindowAttributes: Test 32 -XCreateWindow: Test 30 -XDrawLine: Test 22 -XFillArc: Test 22 -XChangeKeyboardControl: Tests 9, 10 -XRebindKeysym: Test 1 - </verb> - - <sect3>Additional Failures from Xdmx - <p> - When running Xdmx, no unexpected failures were noted. - Since the Xdmx server is based on Xinerama, we expect to - have most of the Xinerama failures present in the Xdmx - server. Similarly, since the Xdmx server must rely on the - low-level device drivers on each back-end server, we also - expect that Xdmx will exhibit most of the back-end - failures. Here is a summary: - <verb> -XListPixmapFormats: Test 1 (configuration dependent) -XChangeWindowAttributes: Test 32 -XCreateWindow: Test 30 -XCopyPlane: Test 13, 22, 31 -XSetFontPath: Test 4 -XGetDefault: Test 5 (configuration dependent) -XMatchVisualInfo: Test 1 -XRebindKeysym: Test 1 (configuration dependent) - </verb> - <p> - Note that this list is shorter than the combined list for - Xinerama because Xdmx uses different code paths to perform - some Xinerama operations. Further, some Xinerama failures - have been fixed in the XFree86 4.2.99.x CVS repository. - - <sect3>Summary and Future Work - <p> - Running the X Test Suite on Xdmx does not produce any - failures that cannot be accounted for by the underlying - Xinerama subsystem used by the front-end or by the - low-level device-driver code running on the back-end X - servers. The Xdmx server therefore is as ``correct'' as - possible with respect to the standard set of X Test Suite - tests. - <p> - During the following phases, we will continue to verify - Xdmx correctness using the X Test Suite. We may also use - other tests suites or write additional tests that run - under the X Test Suite that specifically verify the - expected behavior of DMX. - -<sect2>Fonts - -<p>In Phase I, fonts are handled directly by both the front-end and the -back-end servers, which is required since we must treat each back-end -server during this phase as a ``black box''. What this requires is that -<bf/the front- and back-end servers must share the exact same font -path/. There are two ways to help make sure that all servers share the -same font path: - -<enum> - <item>First, each server can be configured to use the same font - server. The font server, xfs, can be configured to serve fonts to - multiple X servers via TCP. - - <item>Second, each server can be configured to use the same font - path and either those font paths can be copied to each back-end - machine or they can be mounted (e.g., via NFS) on each back-end - machine. -</enum> - -<p>One additional concern is that a client program can set its own font -path, and if it does so, then that font path must be available on each -back-end machine. - -<p>The -fontpath command line option was added to allow users to -initialize the font path of the front end server. This font path is -propagated to each back-end server when the default font is loaded. If -there are any problems, an error message is printed, which will describe -the problem and list the current font path. For more information about -setting the font path, see the -fontpath option description in the man -page. - -<sect2>Performance - -<p>Phase I of development was not intended to optimize performance. Its -focus was on completely and correctly handling the base X11 protocol in -the Xdmx server. However, several insights were gained during Phase I, -which are listed here for reference during the next phase of -development. - -<enum> - <item>Calls to XSync() can slow down rendering since it requires a - complete round trip to and from a back-end server. This is - especially problematic when communicating over long haul networks. - <item>Sending drawing requests to only the screens that they overlap - should improve performance. -</enum> - -<sect2>Pixmaps - -<p>Pixmaps were originally expected to be handled entirely in the -front-end X server; however, it was found that this overly complicated -the rendering code and would have required sending potentially large -images to each back server that required them when copying from pixmap -to screen. Thus, pixmap state is mirrored in the back-end server just -as it is with regular window state. With this implementation, the same -rendering code that draws to windows can be used to draw to pixmaps on -the back-end server, and no large image transfers are required to copy -from pixmap to window. - -<!-- ============================================================ --> -<sect1>Phase II - -<p>The second phase of development concentrates on performance -optimizations. These optimizations are documented here, with -<tt/x11perf/ data to show how the optimizations improve performance. - -<p>All benchmarks were performed by running Xdmx on a dual processor -1.4GHz AMD Athlon machine with 1GB of RAM connecting over 100baseT to -two single-processor 1GHz Pentium III machines with 256MB of RAM and ATI -Rage 128 (RF) video cards. The front end was running Linux -2.4.20-pre1-ac1 and the back ends were running Linux 2.4.7-10 and -version 4.2.99.1 of XFree86 pulled from the XFree86 CVS repository on -August 7, 2002. All systems were running Red Hat Linux 7.2. - -<sect2>Moving from XFree86 4.1.99.1 to 4.2.0.0 - -<p>For phase II, the working source tree was moved to the branch tagged -with dmx-1-0-branch and was updated from version 4.1.99.1 (20 August -2001) of the XFree86 sources to version 4.2.0.0 (18 January 2002). -After this update, the following tests were noted to be more than 10% -faster: - <verb> -1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple) -1.16 Fill 1x1 tiled trapezoid (161x145 tile) -1.13 Fill 10x10 tiled trapezoid (161x145 tile) -1.17 Fill 100x100 tiled trapezoid (161x145 tile) -1.16 Fill 1x1 tiled trapezoid (216x208 tile) -1.20 Fill 10x10 tiled trapezoid (216x208 tile) -1.15 Fill 100x100 tiled trapezoid (216x208 tile) -1.37 Circulate Unmapped window (200 kids) - </verb> -And the following tests were noted to be more than 10% slower: - <verb> -0.88 Unmap window via parent (25 kids) -0.75 Circulate Unmapped window (4 kids) -0.79 Circulate Unmapped window (16 kids) -0.80 Circulate Unmapped window (25 kids) -0.82 Circulate Unmapped window (50 kids) -0.85 Circulate Unmapped window (75 kids) - </verb> -<p>These changes were not caused by any changes in the DMX system, and -may point to changes in the XFree86 tree or to tests that have more -"jitter" than most other <tt/x11perf/ tests. - -<sect2>Global changes - -<p>During the development of the Phase II DMX server, several global -changes were made. These changes were also compared with the Phase I -server. The following tests were noted to be more than 10% faster: - <verb> -1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple) -1.15 Fill 1x1 tiled trapezoid (161x145 tile) -1.13 Fill 10x10 tiled trapezoid (161x145 tile) -1.17 Fill 100x100 tiled trapezoid (161x145 tile) -1.16 Fill 1x1 tiled trapezoid (216x208 tile) -1.19 Fill 10x10 tiled trapezoid (216x208 tile) -1.15 Fill 100x100 tiled trapezoid (216x208 tile) -1.15 Circulate Unmapped window (4 kids) - </verb> - -<p>The following tests were noted to be more than 10% slower: - <verb> -0.69 Scroll 10x10 pixels -0.68 Scroll 100x100 pixels -0.68 Copy 10x10 from window to window -0.68 Copy 100x100 from window to window -0.76 Circulate Unmapped window (75 kids) -0.83 Circulate Unmapped window (100 kids) - </verb> - -<p>For the remainder of this analysis, the baseline of comparison will -be the Phase II deliverable with all optimizations disabled (unless -otherwise noted). This will highlight how the optimizations in -isolation impact performance. - -<sect2>XSync() Batching - -<p>During the Phase I implementation, XSync() was called after every -protocol request made by the DMX server. This provided the DMX server -with an interactive feel, but defeated X11's protocol buffering system -and introduced round-trip wire latency into every operation. During -Phase II, DMX was changed so that protocol requests are no longer -followed by calls to XSync(). Instead, the need for an XSync() is -noted, and XSync() calls are only made every 100mS or when the DMX -server specifically needs to make a call to guarantee interactivity. -With this new system, X11 buffers protocol as much as possible during a -100mS interval, and many unnecessary XSync() calls are avoided. - -<p>Out of more than 300 <tt/x11perf/ tests, 8 tests became more than 100 -times faster, with 68 more than 50X faster, 114 more than 10X faster, -and 181 more than 2X faster. See table below for summary. - -<p>The following tests were noted to be more than 10% slower with -XSync() batching on: - <verb> -0.88 500x500 tiled rectangle (161x145 tile) -0.89 Copy 500x500 from window to window - </verb> - -<sect2>Offscreen Optimization - -<p>Windows span one or more of the back-end servers' screens; however, -during Phase I development, windows were created on every back-end -server and every rendering request was sent to every window regardless -of whether or not that window was visible. With the offscreen -optimization, the DMX server tracks when a window is completely off of a -back-end server's screen and, in that case, it does not send rendering -requests to those back-end windows. This optimization saves bandwidth -between the front and back-end servers, and it reduces the number of -XSync() calls. The performance tests were run on a DMX system with only -two back-end servers. Greater performance gains will be had as the -number of back-end servers increases. - -<p>Out of more than 300 <tt/x11perf/ tests, 3 tests were at least twice as -fast, and 146 tests were at least 10% faster. Two tests were more than -10% slower with the offscreen optimization: - <verb> -0.88 Hide/expose window via popup (4 kids) -0.89 Resize unmapped window (75 kids) - </verb> - -<sect2>Lazy Window Creation Optimization - -<p>As mentioned above, during Phase I, windows were created on every -back-end server even if they were not visible on that back-end. With -the lazy window creation optimization, the DMX server does not create -windows on a back-end server until they are either visible or they -become the parents of a visible window. This optimization builds on the -offscreen optimization (described above) and requires it to be enabled. - -<p>The lazy window creation optimization works by creating the window -data structures in the front-end server when a client creates a window, -but delays creation of the window on the back-end server(s). A private -window structure in the DMX server saves the relevant window data and -tracks changes to the window's attributes and stacking order for later -use. The only times a window is created on a back-end server are (1) -when it is mapped and is at least partially overlapping the back-end -server's screen (tracked by the offscreen optimization), or (2) when the -window becomes the parent of a previously visible window. The first -case occurs when a window is mapped or when a visible window is copied, -moved or resized and now overlaps the back-end server's screen. The -second case occurs when starting a window manager after having created -windows to which the window manager needs to add decorations. - -<p>When either case occurs, a window on the back-end server is created -using the data saved in the DMX server's window private data structure. -The stacking order is then adjusted to correctly place the window on the -back-end and lastly the window is mapped. From this time forward, the -window is handled exactly as if the window had been created at the time -of the client's request. - -<p>Note that when a window is no longer visible on a back-end server's -screen (e.g., it is moved offscreen), the window is not destroyed; -rather, it is kept and reused later if the window once again becomes -visible on the back-end server's screen. Originally with this -optimization, destroying windows was implemented but was later rejected -because it increased bandwidth when windows were opaquely moved or -resized, which is common in many window managers. - -<p>The performance tests were run on a DMX system with only two back-end -servers. Greater performance gains will be had as the number of -back-end servers increases. - -<p>This optimization improved the following <tt/x11perf/ tests by more -than 10%: - <verb> -1.10 500x500 rectangle outline -1.12 Fill 100x100 stippled trapezoid (161x145 stipple) -1.20 Circulate Unmapped window (50 kids) -1.19 Circulate Unmapped window (75 kids) - </verb> - -<sect2>Subdividing Rendering Primitives - -<p>X11 imaging requests transfer significant data between the client and -the X server. During Phase I, the DMX server would then transfer the -image data to each back-end server. Even with the offscreen -optimization (above), these requests still required transferring -significant data to each back-end server that contained a visible -portion of the window. For example, if the client uses XPutImage() to -copy an image to a window that overlaps the entire DMX screen, then the -entire image is copied by the DMX server to every back-end server. - -<p>To reduce the amount of data transferred between the DMX server and -the back-end servers when XPutImage() is called, the image data is -subdivided and only the data that will be visible on a back-end server's -screen is sent to that back-end server. Xinerama already implements a -subdivision algorithm for XGetImage() and no further optimization was -needed. - -<p>Other rendering primitives were analyzed, but the time required to -subdivide these primitives was a significant proportion of the time -required to send the entire rendering request to the back-end server, so -this optimization was rejected for the other rendering primitives. - -<p>Again, the performance tests were run on a DMX system with only two -back-end servers. Greater performance gains will be had as the number -of back-end servers increases. - -<p>This optimization improved the following <tt/x11perf/ tests by more -than 10%: - <verb> -1.12 Fill 100x100 stippled trapezoid (161x145 stipple) -1.26 PutImage 10x10 square -1.83 PutImage 100x100 square -1.91 PutImage 500x500 square -1.40 PutImage XY 10x10 square -1.48 PutImage XY 100x100 square -1.50 PutImage XY 500x500 square -1.45 Circulate Unmapped window (75 kids) -1.74 Circulate Unmapped window (100 kids) - </verb> - -<p>The following test was noted to be more than 10% slower with this -optimization: - <verb> -0.88 10-pixel fill chord partial circle - </verb> - -<sect2>Summary of x11perf Data - -<p>With all of the optimizations on, 53 <tt/x11perf/ tests are more than -100X faster than the unoptimized Phase II deliverable, with 69 more than -50X faster, 73 more than 10X faster, and 199 more than twice as fast. -No tests were more than 10% slower than the unoptimized Phase II -deliverable. (Compared with the Phase I deliverable, only Circulate -Unmapped window (100 kids) was more than 10% slower than the Phase II -deliverable. As noted above, this test seems to have wider variability -than other <tt/x11perf/ tests.) - -<p>The following table summarizes relative <tt/x11perf/ test changes for -all optimizations individually and collectively. Note that some of the -optimizations have a synergistic effect when used together. - <verb> - -1: XSync() batching only -2: Off screen optimizations only -3: Window optimizations only -4: Subdivprims only -5: All optimizations - - 1 2 3 4 5 Operation ------- ---- ---- ---- ------ --------- - 2.14 1.85 1.00 1.00 4.13 Dot - 1.67 1.80 1.00 1.00 3.31 1x1 rectangle - 2.38 1.43 1.00 1.00 2.44 10x10 rectangle - 1.00 1.00 0.92 0.98 1.00 100x100 rectangle - 1.00 1.00 1.00 1.00 1.00 500x500 rectangle - 1.83 1.85 1.05 1.06 3.54 1x1 stippled rectangle (8x8 stipple) - 2.43 1.43 1.00 1.00 2.41 10x10 stippled rectangle (8x8 stipple) - 0.98 1.00 1.00 1.00 1.00 100x100 stippled rectangle (8x8 stipple) - 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (8x8 stipple) - 1.75 1.75 1.00 1.00 3.40 1x1 opaque stippled rectangle (8x8 stipple) - 2.38 1.42 1.00 1.00 2.34 10x10 opaque stippled rectangle (8x8 stipple) - 1.00 1.00 0.97 0.97 1.00 100x100 opaque stippled rectangle (8x8 stipple) - 1.00 1.00 1.00 1.00 0.99 500x500 opaque stippled rectangle (8x8 stipple) - 1.82 1.82 1.04 1.04 3.56 1x1 tiled rectangle (4x4 tile) - 2.33 1.42 1.00 1.00 2.37 10x10 tiled rectangle (4x4 tile) - 1.00 0.92 1.00 1.00 1.00 100x100 tiled rectangle (4x4 tile) - 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (4x4 tile) - 1.94 1.62 1.00 1.00 3.66 1x1 stippled rectangle (17x15 stipple) - 1.74 1.28 1.00 1.00 1.73 10x10 stippled rectangle (17x15 stipple) - 1.00 1.00 1.00 0.89 0.98 100x100 stippled rectangle (17x15 stipple) - 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (17x15 stipple) - 1.94 1.62 1.00 1.00 3.67 1x1 opaque stippled rectangle (17x15 stipple) - 1.69 1.26 1.00 1.00 1.66 10x10 opaque stippled rectangle (17x15 stipple) - 1.00 0.95 1.00 1.00 1.00 100x100 opaque stippled rectangle (17x15 stipple) - 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (17x15 stipple) - 1.93 1.61 0.99 0.99 3.69 1x1 tiled rectangle (17x15 tile) - 1.73 1.27 1.00 1.00 1.72 10x10 tiled rectangle (17x15 tile) - 1.00 1.00 1.00 1.00 0.98 100x100 tiled rectangle (17x15 tile) - 1.00 1.00 0.97 0.97 1.00 500x500 tiled rectangle (17x15 tile) - 1.95 1.63 1.00 1.00 3.83 1x1 stippled rectangle (161x145 stipple) - 1.80 1.30 1.00 1.00 1.83 10x10 stippled rectangle (161x145 stipple) - 0.97 1.00 1.00 1.00 1.01 100x100 stippled rectangle (161x145 stipple) - 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (161x145 stipple) - 1.95 1.63 1.00 1.00 3.56 1x1 opaque stippled rectangle (161x145 stipple) - 1.65 1.25 1.00 1.00 1.68 10x10 opaque stippled rectangle (161x145 stipple) - 1.00 1.00 1.00 1.00 1.01 100x100 opaque stippled rectangle (161x145... - 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (161x145... - 1.95 1.63 0.98 0.99 3.80 1x1 tiled rectangle (161x145 tile) - 1.67 1.26 1.00 1.00 1.67 10x10 tiled rectangle (161x145 tile) - 1.13 1.14 1.14 1.14 1.14 100x100 tiled rectangle (161x145 tile) - 0.88 1.00 1.00 1.00 0.99 500x500 tiled rectangle (161x145 tile) - 1.93 1.63 1.00 1.00 3.53 1x1 tiled rectangle (216x208 tile) - 1.69 1.26 1.00 1.00 1.66 10x10 tiled rectangle (216x208 tile) - 1.00 1.00 1.00 1.00 1.00 100x100 tiled rectangle (216x208 tile) - 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (216x208 tile) - 1.82 1.70 1.00 1.00 3.38 1-pixel line segment - 2.07 1.56 0.90 1.00 3.31 10-pixel line segment - 1.29 1.10 1.00 1.00 1.27 100-pixel line segment - 1.05 1.06 1.03 1.03 1.09 500-pixel line segment - 1.30 1.13 1.00 1.00 1.29 100-pixel line segment (1 kid) - 1.32 1.15 1.00 1.00 1.32 100-pixel line segment (2 kids) - 1.33 1.16 1.00 1.00 1.33 100-pixel line segment (3 kids) - 1.92 1.64 1.00 1.00 3.73 10-pixel dashed segment - 1.34 1.16 1.00 1.00 1.34 100-pixel dashed segment - 1.24 1.11 0.99 0.97 1.23 100-pixel double-dashed segment - 1.72 1.77 1.00 1.00 3.25 10-pixel horizontal line segment - 1.83 1.66 1.01 1.00 3.54 100-pixel horizontal line segment - 1.86 1.30 1.00 1.00 1.84 500-pixel horizontal line segment - 2.11 1.52 1.00 0.99 3.02 10-pixel vertical line segment - 1.21 1.10 1.00 1.00 1.20 100-pixel vertical line segment - 1.03 1.03 1.00 1.00 1.02 500-pixel vertical line segment - 4.42 1.68 1.00 1.01 4.64 10x1 wide horizontal line segment - 1.83 1.31 1.00 1.00 1.83 100x10 wide horizontal line segment - 1.07 1.00 0.96 1.00 1.07 500x50 wide horizontal line segment - 4.10 1.67 1.00 1.00 4.62 10x1 wide vertical line segment - 1.50 1.24 1.06 1.06 1.48 100x10 wide vertical line segment - 1.06 1.03 1.00 1.00 1.05 500x50 wide vertical line segment - 2.54 1.61 1.00 1.00 3.61 1-pixel line - 2.71 1.48 1.00 1.00 2.67 10-pixel line - 1.19 1.09 1.00 1.00 1.19 100-pixel line - 1.04 1.02 1.00 1.00 1.03 500-pixel line - 2.68 1.51 0.98 1.00 3.17 10-pixel dashed line - 1.23 1.11 0.99 0.99 1.23 100-pixel dashed line - 1.15 1.08 1.00 1.00 1.15 100-pixel double-dashed line - 2.27 1.39 1.00 1.00 2.23 10x1 wide line - 1.20 1.09 1.00 1.00 1.20 100x10 wide line - 1.04 1.02 1.00 1.00 1.04 500x50 wide line - 1.52 1.45 1.00 1.00 1.52 100x10 wide dashed line - 1.54 1.47 1.00 1.00 1.54 100x10 wide double-dashed line - 1.97 1.30 0.96 0.95 1.95 10x10 rectangle outline - 1.44 1.27 1.00 1.00 1.43 100x100 rectangle outline - 3.22 2.16 1.10 1.09 3.61 500x500 rectangle outline - 1.95 1.34 1.00 1.00 1.90 10x10 wide rectangle outline - 1.14 1.14 1.00 1.00 1.13 100x100 wide rectangle outline - 1.00 1.00 1.00 1.00 1.00 500x500 wide rectangle outline - 1.57 1.72 1.00 1.00 3.03 1-pixel circle - 1.96 1.35 1.00 1.00 1.92 10-pixel circle - 1.21 1.07 0.86 0.97 1.20 100-pixel circle - 1.08 1.04 1.00 1.00 1.08 500-pixel circle - 1.39 1.19 1.03 1.03 1.38 100-pixel dashed circle - 1.21 1.11 1.00 1.00 1.23 100-pixel double-dashed circle - 1.59 1.28 1.00 1.00 1.58 10-pixel wide circle - 1.22 1.12 0.99 1.00 1.22 100-pixel wide circle - 1.06 1.04 1.00 1.00 1.05 500-pixel wide circle - 1.87 1.84 1.00 1.00 1.85 100-pixel wide dashed circle - 1.90 1.93 1.01 1.01 1.90 100-pixel wide double-dashed circle - 2.13 1.43 1.00 1.00 2.32 10-pixel partial circle - 1.42 1.18 1.00 1.00 1.42 100-pixel partial circle - 1.92 1.85 1.01 1.01 1.89 10-pixel wide partial circle - 1.73 1.67 1.00 1.00 1.73 100-pixel wide partial circle - 1.36 1.95 1.00 1.00 2.64 1-pixel solid circle - 2.02 1.37 1.00 1.00 2.03 10-pixel solid circle - 1.19 1.09 1.00 1.00 1.19 100-pixel solid circle - 1.02 0.99 1.00 1.00 1.01 500-pixel solid circle - 1.74 1.28 1.00 0.88 1.73 10-pixel fill chord partial circle - 1.31 1.13 1.00 1.00 1.31 100-pixel fill chord partial circle - 1.67 1.31 1.03 1.03 1.72 10-pixel fill slice partial circle - 1.30 1.13 1.00 1.00 1.28 100-pixel fill slice partial circle - 2.45 1.49 1.01 1.00 2.71 10-pixel ellipse - 1.22 1.10 1.00 1.00 1.22 100-pixel ellipse - 1.09 1.04 1.00 1.00 1.09 500-pixel ellipse - 1.90 1.28 1.00 1.00 1.89 100-pixel dashed ellipse - 1.62 1.24 0.96 0.97 1.61 100-pixel double-dashed ellipse - 2.43 1.50 1.00 1.00 2.42 10-pixel wide ellipse - 1.61 1.28 1.03 1.03 1.60 100-pixel wide ellipse - 1.08 1.05 1.00 1.00 1.08 500-pixel wide ellipse - 1.93 1.88 1.00 1.00 1.88 100-pixel wide dashed ellipse - 1.94 1.89 1.01 1.00 1.94 100-pixel wide double-dashed ellipse - 2.31 1.48 1.00 1.00 2.67 10-pixel partial ellipse - 1.38 1.17 1.00 1.00 1.38 100-pixel partial ellipse - 2.00 1.85 0.98 0.97 1.98 10-pixel wide partial ellipse - 1.89 1.86 1.00 1.00 1.89 100-pixel wide partial ellipse - 3.49 1.60 1.00 1.00 3.65 10-pixel filled ellipse - 1.67 1.26 1.00 1.00 1.67 100-pixel filled ellipse - 1.06 1.04 1.00 1.00 1.06 500-pixel filled ellipse - 2.38 1.43 1.01 1.00 2.32 10-pixel fill chord partial ellipse - 2.06 1.30 1.00 1.00 2.05 100-pixel fill chord partial ellipse - 2.27 1.41 1.00 1.00 2.27 10-pixel fill slice partial ellipse - 1.98 1.33 1.00 0.97 1.97 100-pixel fill slice partial ellipse - 57.46 1.99 1.01 1.00 114.92 Fill 1x1 equivalent triangle - 56.94 1.98 1.01 1.00 73.89 Fill 10x10 equivalent triangle - 6.07 1.75 1.00 1.00 6.07 Fill 100x100 equivalent triangle - 51.12 1.98 1.00 1.00 102.81 Fill 1x1 trapezoid - 51.42 1.82 1.01 1.00 94.89 Fill 10x10 trapezoid - 6.47 1.80 1.00 1.00 6.44 Fill 100x100 trapezoid - 1.56 1.28 1.00 0.99 1.56 Fill 300x300 trapezoid - 51.27 1.97 0.96 0.97 102.54 Fill 1x1 stippled trapezoid (8x8 stipple) - 51.73 2.00 1.02 1.02 67.92 Fill 10x10 stippled trapezoid (8x8 stipple) - 5.36 1.72 1.00 1.00 5.36 Fill 100x100 stippled trapezoid (8x8 stipple) - 1.54 1.26 1.00 1.00 1.59 Fill 300x300 stippled trapezoid (8x8 stipple) - 51.41 1.94 1.01 1.00 102.82 Fill 1x1 opaque stippled trapezoid (8x8 stipple) - 50.71 1.95 0.99 1.00 65.44 Fill 10x10 opaque stippled trapezoid (8x8... - 5.33 1.73 1.00 1.00 5.36 Fill 100x100 opaque stippled trapezoid (8x8... - 1.58 1.25 1.00 1.00 1.58 Fill 300x300 opaque stippled trapezoid (8x8... - 51.56 1.96 0.99 0.90 103.68 Fill 1x1 tiled trapezoid (4x4 tile) - 51.59 1.99 1.01 1.01 62.25 Fill 10x10 tiled trapezoid (4x4 tile) - 5.38 1.72 1.00 1.00 5.38 Fill 100x100 tiled trapezoid (4x4 tile) - 1.54 1.25 1.00 0.99 1.58 Fill 300x300 tiled trapezoid (4x4 tile) - 51.70 1.98 1.01 1.01 103.98 Fill 1x1 stippled trapezoid (17x15 stipple) - 44.86 1.97 1.00 1.00 44.86 Fill 10x10 stippled trapezoid (17x15 stipple) - 2.74 1.56 1.00 1.00 2.73 Fill 100x100 stippled trapezoid (17x15 stipple) - 1.29 1.14 1.00 1.00 1.27 Fill 300x300 stippled trapezoid (17x15 stipple) - 51.41 1.96 0.96 0.95 103.39 Fill 1x1 opaque stippled trapezoid (17x15... - 45.14 1.96 1.01 1.00 45.14 Fill 10x10 opaque stippled trapezoid (17x15... - 2.68 1.56 1.00 1.00 2.68 Fill 100x100 opaque stippled trapezoid (17x15... - 1.26 1.10 1.00 1.00 1.28 Fill 300x300 opaque stippled trapezoid (17x15... - 51.13 1.97 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (17x15 tile) - 47.58 1.96 1.00 1.00 47.86 Fill 10x10 tiled trapezoid (17x15 tile) - 2.74 1.56 1.00 1.00 2.74 Fill 100x100 tiled trapezoid (17x15 tile) - 1.29 1.14 1.00 1.00 1.28 Fill 300x300 tiled trapezoid (17x15 tile) - 51.13 1.97 0.99 0.97 103.39 Fill 1x1 stippled trapezoid (161x145 stipple) - 45.14 1.97 1.00 1.00 44.29 Fill 10x10 stippled trapezoid (161x145 stipple) - 3.02 1.77 1.12 1.12 3.38 Fill 100x100 stippled trapezoid (161x145 stipple) - 1.31 1.13 1.00 1.00 1.30 Fill 300x300 stippled trapezoid (161x145 stipple) - 51.27 1.97 1.00 1.00 103.10 Fill 1x1 opaque stippled trapezoid (161x145... - 45.01 1.97 1.00 1.00 45.01 Fill 10x10 opaque stippled trapezoid (161x145... - 2.67 1.56 1.00 1.00 2.69 Fill 100x100 opaque stippled trapezoid (161x145.. - 1.29 1.13 1.00 1.01 1.27 Fill 300x300 opaque stippled trapezoid (161x145.. - 51.41 1.96 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (161x145 tile) - 45.01 1.96 0.98 1.00 45.01 Fill 10x10 tiled trapezoid (161x145 tile) - 2.62 1.36 1.00 1.00 2.69 Fill 100x100 tiled trapezoid (161x145 tile) - 1.27 1.13 1.00 1.00 1.22 Fill 300x300 tiled trapezoid (161x145 tile) - 51.13 1.98 1.00 1.00 103.39 Fill 1x1 tiled trapezoid (216x208 tile) - 45.14 1.97 1.01 0.99 45.14 Fill 10x10 tiled trapezoid (216x208 tile) - 2.62 1.55 1.00 1.00 2.71 Fill 100x100 tiled trapezoid (216x208 tile) - 1.28 1.13 1.00 1.00 1.20 Fill 300x300 tiled trapezoid (216x208 tile) - 50.71 1.95 1.00 1.00 54.70 Fill 10x10 equivalent complex polygon - 5.51 1.71 0.96 0.98 5.47 Fill 100x100 equivalent complex polygons - 8.39 1.97 1.00 1.00 16.75 Fill 10x10 64-gon (Convex) - 8.38 1.83 1.00 1.00 8.43 Fill 100x100 64-gon (Convex) - 8.50 1.96 1.00 1.00 16.64 Fill 10x10 64-gon (Complex) - 8.26 1.83 1.00 1.00 8.35 Fill 100x100 64-gon (Complex) - 14.09 1.87 1.00 1.00 14.05 Char in 80-char line (6x13) - 11.91 1.87 1.00 1.00 11.95 Char in 70-char line (8x13) - 11.16 1.85 1.01 1.00 11.10 Char in 60-char line (9x15) - 10.09 1.78 1.00 1.00 10.09 Char16 in 40-char line (k14) - 6.15 1.75 1.00 1.00 6.31 Char16 in 23-char line (k24) - 11.92 1.90 1.03 1.03 11.88 Char in 80-char line (TR 10) - 8.18 1.78 1.00 0.99 8.17 Char in 30-char line (TR 24) - 42.83 1.44 1.01 1.00 42.11 Char in 20/40/20 line (6x13, TR 10) - 27.45 1.43 1.01 1.01 27.45 Char16 in 7/14/7 line (k14, k24) - 12.13 1.85 1.00 1.00 12.05 Char in 80-char image line (6x13) - 10.00 1.84 1.00 1.00 10.00 Char in 70-char image line (8x13) - 9.18 1.83 1.00 1.00 9.12 Char in 60-char image line (9x15) - 9.66 1.82 0.98 0.95 9.66 Char16 in 40-char image line (k14) - 5.82 1.72 1.00 1.00 5.99 Char16 in 23-char image line (k24) - 8.70 1.80 1.00 1.00 8.65 Char in 80-char image line (TR 10) - 4.67 1.66 1.00 1.00 4.67 Char in 30-char image line (TR 24) - 84.43 1.47 1.00 1.00 124.18 Scroll 10x10 pixels - 3.73 1.50 1.00 0.98 3.73 Scroll 100x100 pixels - 1.00 1.00 1.00 1.00 1.00 Scroll 500x500 pixels - 84.43 1.51 1.00 1.00 134.02 Copy 10x10 from window to window - 3.62 1.51 0.98 0.98 3.62 Copy 100x100 from window to window - 0.89 1.00 1.00 1.00 1.00 Copy 500x500 from window to window - 57.06 1.99 1.00 1.00 88.64 Copy 10x10 from pixmap to window - 2.49 2.00 1.00 1.00 2.48 Copy 100x100 from pixmap to window - 1.00 0.91 1.00 1.00 0.98 Copy 500x500 from pixmap to window - 2.04 1.01 1.00 1.00 2.03 Copy 10x10 from window to pixmap - 1.05 1.00 1.00 1.00 1.05 Copy 100x100 from window to pixmap - 1.00 1.00 0.93 1.00 1.04 Copy 500x500 from window to pixmap - 58.52 1.03 1.03 1.02 57.95 Copy 10x10 from pixmap to pixmap - 2.40 1.00 1.00 1.00 2.45 Copy 100x100 from pixmap to pixmap - 1.00 1.00 1.00 1.00 1.00 Copy 500x500 from pixmap to pixmap - 51.57 1.92 1.00 1.00 85.75 Copy 10x10 1-bit deep plane - 6.37 1.75 1.01 1.01 6.37 Copy 100x100 1-bit deep plane - 1.26 1.11 1.00 1.00 1.24 Copy 500x500 1-bit deep plane - 4.23 1.63 0.98 0.97 4.38 Copy 10x10 n-bit deep plane - 1.04 1.02 1.00 1.00 1.04 Copy 100x100 n-bit deep plane - 1.00 1.00 1.00 1.00 1.00 Copy 500x500 n-bit deep plane - 6.45 1.98 1.00 1.26 12.80 PutImage 10x10 square - 1.10 1.87 1.00 1.83 2.11 PutImage 100x100 square - 1.02 1.93 1.00 1.91 1.91 PutImage 500x500 square - 4.17 1.78 1.00 1.40 7.18 PutImage XY 10x10 square - 1.27 1.49 0.97 1.48 2.10 PutImage XY 100x100 square - 1.00 1.50 1.00 1.50 1.52 PutImage XY 500x500 square - 1.07 1.01 1.00 1.00 1.06 GetImage 10x10 square - 1.01 1.00 1.00 1.00 1.01 GetImage 100x100 square - 1.00 1.00 1.00 1.00 1.00 GetImage 500x500 square - 1.56 1.00 0.99 0.97 1.56 GetImage XY 10x10 square - 1.02 1.00 1.00 1.00 1.02 GetImage XY 100x100 square - 1.00 1.00 1.00 1.00 1.00 GetImage XY 500x500 square - 1.00 1.00 1.01 0.98 0.95 X protocol NoOperation - 1.02 1.03 1.04 1.03 1.00 QueryPointer - 1.03 1.02 1.04 1.03 1.00 GetProperty -100.41 1.51 1.00 1.00 198.76 Change graphics context - 45.81 1.00 0.99 0.97 57.10 Create and map subwindows (4 kids) - 78.45 1.01 1.02 1.02 63.07 Create and map subwindows (16 kids) - 73.91 1.01 1.00 1.00 56.37 Create and map subwindows (25 kids) - 73.22 1.00 1.00 1.00 49.07 Create and map subwindows (50 kids) - 72.36 1.01 0.99 1.00 32.14 Create and map subwindows (75 kids) - 70.34 1.00 1.00 1.00 30.12 Create and map subwindows (100 kids) - 55.00 1.00 1.00 0.99 23.75 Create and map subwindows (200 kids) - 55.30 1.01 1.00 1.00 141.03 Create unmapped window (4 kids) - 55.38 1.01 1.01 1.00 163.25 Create unmapped window (16 kids) - 54.75 0.96 1.00 0.99 166.95 Create unmapped window (25 kids) - 54.83 1.00 1.00 0.99 178.81 Create unmapped window (50 kids) - 55.38 1.01 1.01 1.00 181.20 Create unmapped window (75 kids) - 55.38 1.01 1.01 1.00 181.20 Create unmapped window (100 kids) - 54.87 1.01 1.01 1.00 182.05 Create unmapped window (200 kids) - 28.13 1.00 1.00 1.00 30.75 Map window via parent (4 kids) - 36.14 1.01 1.01 1.01 32.58 Map window via parent (16 kids) - 26.13 1.00 0.98 0.95 29.85 Map window via parent (25 kids) - 40.07 1.00 1.01 1.00 27.57 Map window via parent (50 kids) - 23.26 0.99 1.00 1.00 18.23 Map window via parent (75 kids) - 22.91 0.99 1.00 0.99 16.52 Map window via parent (100 kids) - 27.79 1.00 1.00 0.99 12.50 Map window via parent (200 kids) - 22.35 1.00 1.00 1.00 56.19 Unmap window via parent (4 kids) - 9.57 1.00 0.99 1.00 89.78 Unmap window via parent (16 kids) - 80.77 1.01 1.00 1.00 103.85 Unmap window via parent (25 kids) - 96.34 1.00 1.00 1.00 116.06 Unmap window via parent (50 kids) - 99.72 1.00 1.00 1.00 124.93 Unmap window via parent (75 kids) -112.36 1.00 1.00 1.00 125.27 Unmap window via parent (100 kids) -105.41 1.00 1.00 0.99 120.00 Unmap window via parent (200 kids) - 51.29 1.03 1.02 1.02 74.19 Destroy window via parent (4 kids) - 86.75 0.99 0.99 0.99 116.87 Destroy window via parent (16 kids) -106.43 1.01 1.01 1.01 127.49 Destroy window via parent (25 kids) -120.34 1.01 1.01 1.00 140.11 Destroy window via parent (50 kids) -126.67 1.00 0.99 0.99 145.00 Destroy window via parent (75 kids) -126.11 1.01 1.01 1.00 140.56 Destroy window via parent (100 kids) -128.57 1.01 1.00 1.00 137.91 Destroy window via parent (200 kids) - 16.04 0.88 1.00 1.00 20.36 Hide/expose window via popup (4 kids) - 19.04 1.01 1.00 1.00 23.48 Hide/expose window via popup (16 kids) - 19.22 1.00 1.00 1.00 20.44 Hide/expose window via popup (25 kids) - 17.41 1.00 0.91 0.97 17.68 Hide/expose window via popup (50 kids) - 17.29 1.01 1.00 1.01 17.07 Hide/expose window via popup (75 kids) - 16.74 1.00 1.00 1.00 16.17 Hide/expose window via popup (100 kids) - 10.30 1.00 1.00 1.00 10.51 Hide/expose window via popup (200 kids) - 16.48 1.01 1.00 1.00 26.05 Move window (4 kids) - 17.01 0.95 1.00 1.00 23.97 Move window (16 kids) - 16.95 1.00 1.00 1.00 22.90 Move window (25 kids) - 16.05 1.01 1.00 1.00 21.32 Move window (50 kids) - 15.58 1.00 0.98 0.98 19.44 Move window (75 kids) - 14.98 1.02 1.03 1.03 18.17 Move window (100 kids) - 10.90 1.01 1.01 1.00 12.68 Move window (200 kids) - 49.42 1.00 1.00 1.00 198.27 Moved unmapped window (4 kids) - 50.72 0.97 1.00 1.00 193.66 Moved unmapped window (16 kids) - 50.87 1.00 0.99 1.00 195.09 Moved unmapped window (25 kids) - 50.72 1.00 1.00 1.00 189.34 Moved unmapped window (50 kids) - 50.87 1.00 1.00 1.00 191.33 Moved unmapped window (75 kids) - 50.87 1.00 1.00 0.90 186.71 Moved unmapped window (100 kids) - 50.87 1.00 1.00 1.00 179.19 Moved unmapped window (200 kids) - 41.04 1.00 1.00 1.00 56.61 Move window via parent (4 kids) - 69.81 1.00 1.00 1.00 130.82 Move window via parent (16 kids) - 95.81 1.00 1.00 1.00 141.92 Move window via parent (25 kids) - 95.98 1.00 1.00 1.00 149.43 Move window via parent (50 kids) - 96.59 1.01 1.01 1.00 153.98 Move window via parent (75 kids) - 97.19 1.00 1.00 1.00 157.30 Move window via parent (100 kids) - 96.67 1.00 0.99 0.96 159.44 Move window via parent (200 kids) - 17.75 1.01 1.00 1.00 27.61 Resize window (4 kids) - 17.94 1.00 1.00 0.99 25.42 Resize window (16 kids) - 17.92 1.01 1.00 1.00 24.47 Resize window (25 kids) - 17.24 0.97 1.00 1.00 24.14 Resize window (50 kids) - 16.81 1.00 1.00 0.99 22.75 Resize window (75 kids) - 16.08 1.00 1.00 1.00 21.20 Resize window (100 kids) - 12.92 1.00 0.99 1.00 16.26 Resize window (200 kids) - 52.94 1.01 1.00 1.00 327.12 Resize unmapped window (4 kids) - 53.60 1.01 1.01 1.01 333.71 Resize unmapped window (16 kids) - 52.99 1.00 1.00 1.00 337.29 Resize unmapped window (25 kids) - 51.98 1.00 1.00 1.00 329.38 Resize unmapped window (50 kids) - 53.05 0.89 1.00 1.00 322.60 Resize unmapped window (75 kids) - 53.05 1.00 1.00 1.00 318.08 Resize unmapped window (100 kids) - 53.11 1.00 1.00 0.99 306.21 Resize unmapped window (200 kids) - 16.76 1.00 0.96 1.00 19.46 Circulate window (4 kids) - 17.24 1.00 1.00 0.97 16.24 Circulate window (16 kids) - 16.30 1.03 1.03 1.03 15.85 Circulate window (25 kids) - 13.45 1.00 1.00 1.00 14.90 Circulate window (50 kids) - 12.91 1.00 1.00 1.00 13.06 Circulate window (75 kids) - 11.30 0.98 1.00 1.00 11.03 Circulate window (100 kids) - 7.58 1.01 1.01 0.99 7.47 Circulate window (200 kids) - 1.01 1.01 0.98 1.00 0.95 Circulate Unmapped window (4 kids) - 1.07 1.07 1.01 1.07 1.02 Circulate Unmapped window (16 kids) - 1.04 1.09 1.06 1.05 0.97 Circulate Unmapped window (25 kids) - 1.04 1.23 1.20 1.18 1.05 Circulate Unmapped window (50 kids) - 1.18 1.53 1.19 1.45 1.24 Circulate Unmapped window (75 kids) - 1.08 1.02 1.01 1.74 1.01 Circulate Unmapped window (100 kids) - 1.01 1.12 0.98 0.91 0.97 Circulate Unmapped window (200 kids) - </verb> - -<sect2>Profiling with OProfile - -<p>OProfile (available from http://oprofile.sourceforge.net/) is a -system-wide profiler for Linux systems that uses processor-level -counters to collect sampling data. OProfile can provide information -that is similar to that provided by <tt/gprof/, but without the -necessity of recompiling the program with special instrumentation (i.e., -OProfile can collect statistical profiling information about optimized -programs). A test harness was developed to collect OProfile data for -each <tt/x11perf/ test individually. - -<p>Test runs were performed using the RETIRED_INSNS counter on the AMD -Athlon and the CPU_CLK_HALTED counter on the Intel Pentium III (with a -test configuration different from the one described above). We have -examined OProfile output and have compared it with <tt/gprof/ output. -This investigation has not produced results that yield performance -increases in <tt/x11perf/ numbers. - -<!-- -<sect3>Retired Instructions - -<p>The initial tests using OProfile were done using the RETIRED_INSNS -counter with DMX running on the dual-processor AMD Athlon machine - the -same test configuration that was described above and that was used for -other tests. The RETIRED_INSNS counter counts retired instructions and -showed drawing, text, copying, and image tests to be dominated (> -30%) by calls to Hash(), SecurityLookupIDByClass(), -SecurityLookupIDByType(), and StandardReadRequestFromClient(). Some of -these tests also executed significant instructions in -WaitForSomething(). - -<p>In contrast, the window tests executed significant -instructions in SecurityLookupIDByType(), Hash(), -StandardReadRequestFromClient(), but also executed significant -instructions in other routines, such as ConfigureWindow(). Some time -was spent looking at Hash() function, but optimizations in this routine -did not lead to a dramatic increase in <tt/x11perf/ performance. ---> - -<!-- -<sect3>Clock Cycles - -<p>Retired instructions can be misleading because Intel/AMD instructions -execute in variable amounts of time. The OProfile tests were repeated -using the Intel CPU_CLK_HALTED counter with DMX running on the second -back-end machine. Note that this is a different test configuration that -the one described above. However, these tests show the amount of time -(as measured in CPU cycles) that are spent in each routine. Because -<tt/x11perf/ was running on the first back-end machine and because -window optimizations were on, the load on the second back-end machine -was not significant. - -<p>Using CPU_CLK_HALTED, DMX showed simple drawing -tests spending more than 10% of their time in -StandardReadRequestFromClient(), with significant time (> 20% total) -spent in SecurityLookupIDByClass(), WaitForSomething(), and Dispatch(). -For these tests, < 5% of the time was spent in Hash(), which explains -why optimizing the Hash() routine did not impact <tt/x11perf/ results. - -<p>The trapezoid, text, scrolling, copying, and image tests were -dominated by time in ProcFillPoly(), PanoramiXFillPoly(), dmxFillPolygon(), -SecurityLookupIDByClass(), SecurityLookupIDByType(), and -StandardReadRequestFromClient(). Hash() time was generally above 5% but -less than 10% of total time. ---> - -<sect2>X Test Suite - -<p>The X Test Suite was run on the fully optimized DMX server using the -configuration described above. The following failures were noted: - <verb> -XListPixmapFormats: Test 1 [1] -XChangeWindowAttributes: Test 32 [1] -XCreateWindow: Test 30 [1] -XFreeColors: Test 4 [3] -XCopyArea: Test 13, 17, 21, 25, 30 [2] -XCopyPlane: Test 11, 15, 27, 31 [2] -XSetFontPath: Test 4 [1] -XChangeKeyboardControl: Test 9, 10 [1] - -[1] Previously documented errors expected from the Xinerama - implementation (see Phase I discussion). -[2] Newly noted errors that have been verified as expected - behavior of the Xinerama implementation. -[3] Newly noted error that has been verified as a Xinerama - implementation bug. - </verb> - -<!-- ============================================================ --> -<sect1>Phase III - -<p>During the third phase of development, support was provided for the -following extensions: SHAPE, RENDER, XKEYBOARD, XInput. - -<sect2>SHAPE - -<p>The SHAPE extension is supported. Test applications (e.g., xeyes and -oclock) and window managers that make use of the SHAPE extension will -work as expected. - -<sect2>RENDER - -<p>The RENDER extension is supported. The version included in the DMX -CVS tree is version 0.2, and this version is fully supported by Xdmx. -Applications using only version 0.2 functions will work correctly; -however, some apps that make use of functions from later versions do not -properly check the extension's major/minor version numbers. These apps -will fail with a Bad Implementation error when using post-version 0.2 -functions. This is expected behavior. When the DMX CVS tree is updated -to include newer versions of RENDER, support for these newer functions -will be added to the DMX X server. - -<sect2>XKEYBOARD - -<p>The XKEYBOARD extension is supported. If present on the back-end X -servers, the XKEYBOARD extension will be used to obtain information -about the type of the keyboard for initialization. Otherwise, the -keyboard will be initialized using defaults. Note that this departs -from older behavior: when Xdmx is compiled without XKEYBOARD support, -the map from the back-end X server will be preserved. With XKEYBOARD -support, the map is not preserved because better information and control -of the keyboard is available. - -<sect2>XInput - -<p>The XInput extension is supported. Any device can be used as a core -device and be used as an XInput extension device, with the exception of -core devices on the back-end servers. This limitation is present -because cursor handling on the back-end requires that the back-end -cursor sometimes track the Xdmx core cursor -- behavior that is -incompatible with using the back-end pointer as a non-core device. - -<p>Currently, back-end extension devices are not available as Xdmx -extension devices, but this limitation should be removed in the future. - -<p>To demonstrate the XInput extension, and to provide more examples for -low-level input device driver writers, USB device drivers have been -written for mice (usb-mou), keyboards (usb-kbd), and -non-mouse/non-keyboard USB devices (usb-oth). Please see the man page -for information on Linux kernel drivers that are required for using -these Xdmx drivers. - -<sect2>DPMS - -<p>The DPMS extension is exported but does not do anything at this time. - -<sect2>Other Extensions - -<p>The LBX, - SECURITY, - XC-APPGROUP, and - XFree86-Bigfont -extensions do not require any special Xdmx support and have been exported. - -<p>The - BIG-REQUESTS, - DEC-XTRAP, - DOUBLE-BUFFER, - Extended-Visual-Information, - FontCache, - GLX, - MIT-SCREEN-SAVER, - MIT-SHM, - MIT-SUNDRY-NONSTANDARD, - RECORD, - SECURITY, - SGI-GLX, - SYNC, - TOG-CUP, - X-Resource, - XC-MISC, - XFree86-DGA, - XFree86-DRI, - XFree86-Misc, - XFree86-VidModeExtension, and - XVideo -extensions are <it/not/ supported at this time, but will be evaluated -for inclusion in future DMX releases. <bf>See below for additional work -on extensions after Phase III.</bf> - -<sect1>Phase IV - -<sect2>Moving to XFree86 4.3.0 - -<p>For Phase IV, the recent release of XFree86 4.3.0 (27 February 2003) -was merged onto the dmx.sourceforge.net CVS trunk and all work is -proceeding using this tree. - -<sect2>Extensions - -<sect3>XC-MISC (supported) - -<p>XC-MISC is used internally by the X library to recycle XIDs from the -X server. This is important for long-running X server sessions. Xdmx -supports this extension. The X Test Suite passed and failed the exact -same tests before and after this extension was enabled. -<!-- Tested February/March 2003 --> - -<sect3>Extended-Visual-Information (supported) - -<p>The Extended-Visual-Information extension provides a method for an X -client to obtain detailed visual information. Xdmx supports this -extension. It was tested using the <tt>hw/dmx/examples/evi</tt> example -program. <bf/Note that this extension is not Xinerama-aware/ -- it will -return visual information for each screen even though Xinerama is -causing the X server to export a single logical screen. -<!-- Tested March 2003 --> - -<sect3>RES (supported) - -<p>The X-Resource extension provides a mechanism for a client to obtain -detailed information about the resources used by other clients. This -extension was tested with the <tt>hw/dmx/examples/res</tt> program. The -X Test Suite passed and failed the exact same tests before and after -this extension was enabled. -<!-- Tested March 2003 --> - -<sect3>BIG-REQUESTS (supported) - -<p>This extension enables the X11 protocol to handle requests longer -than 262140 bytes. The X Test Suite passed and failed the exact same -tests before and after this extension was enabled. -<!-- Tested March 2003 --> - -<sect3>XSYNC (supported) - -<p>This extension provides facilities for two different X clients to -synchronize their requests. This extension was minimally tested with -<tt/xdpyinfo/ and the X Test Suite passed and failed the exact same -tests before and after this extension was enabled. -<!-- Tested March 2003 --> - -<sect3>XTEST, RECORD, DEC-XTRAP (supported) and XTestExtension1 (not supported) - -<p>The XTEST and RECORD extension were developed by the X Consortium for -use in the X Test Suite and are supported as a standard in the X11R6 -tree. They are also supported in Xdmx. When X Test Suite tests that -make use of the XTEST extension are run, Xdmx passes and fails exactly -the same tests as does a standard XFree86 X server. When the -<tt/rcrdtest/ test (a part of the X Test Suite that verifies the RECORD -extension) is run, Xdmx passes and fails exactly the same tests as does -a standard XFree86 X server. <!-- Tested February/March 2003 --> - -<p>There are two older XTEST-like extensions: DEC-XTRAP and -XTestExtension1. The XTestExtension1 extension was developed for use by -the X Testing Consortium for use with a test suite that eventually -became (part of?) the X Test Suite. Unlike XTEST, which only allows -events to be sent to the server, the XTestExtension1 extension also -allowed events to be recorded (similar to the RECORD extension). The -second is the DEC-XTRAP extension that was developed by the Digital -Equipment Corporation. - -<p>The DEC-XTRAP extension is available from Xdmx and has been tested -with the <tt/xtrap*/ tools which are distributed as standard X11R6 -clients. <!-- Tested March 2003 --> - -<p>The XTestExtension1 is <em/not/ supported because it does not appear -to be used by any modern X clients (the few that support it also support -XTEST) and because there are no good methods available for testing that -it functions correctly (unlike XTEST and DEC-XTRAP, the code for -XTestExtension1 is not part of the standard X server source tree, so -additional testing is important). <!-- Tested March 2003 --> - -<p>Most of these extensions are documented in the X11R6 source tree. -Further, several original papers exist that this author was unable to -locate -- for completeness and historical interest, citations are -provide: -<descrip> -<tag/XRECORD/ Martha Zimet. Extending X For Recording. 8th Annual X -Technical Conference Boston, MA January 24-26, 1994. -<tag/DEC-XTRAP/ Dick Annicchiarico, Robert Chesler, Alan Jamison. XTrap -Architecture. Digital Equipment Corporation, July 1991. -<tag/XTestExtension1/ Larry Woestman. X11 Input Synthesis Extension -Proposal. Hewlett Packard, November 1991. -</descrip> - -<sect3>MIT-MISC (not supported) - -<p>The MIT-MISC extension is used to control a bug-compatibility flag -that provides compatibility with xterm programs from X11R1 and X11R2. -There does not appear to be a single client available that makes use of -this extension and there is not way to verify that it works correctly. -The Xdmx server does <em/not/ support MIT-MISC. - -<sect3>SCREENSAVER (not supported) - -<p>This extension provides special support for the X screen saver. It -was tested with beforelight, which appears to be the only client that -works with it. When Xinerama was not active, <tt/beforelight/ behaved -as expected. However, when Xinerama was active, <tt/beforelight/ did -not behave as expected. Further, when this extension is not active, -<tt/xscreensaver/ (a widely-used X screen saver program) did not behave -as expected. Since this extension is not Xinerama-aware and is not -commonly used with expected results by clients, we have left this -extension disabled at this time. - -<sect3>GLX (supported) - -<p>The GLX extension provides OpenGL and GLX windowing support. In -Xdmx, the extension is called glxProxy, and it is Xinerama aware. It -works by either feeding requests forward through Xdmx to each of the -back-end servers or handling them locally. All rendering requests are -handled on the back-end X servers. This code was donated to the DMX -project by SGI. For the X Test Suite results comparison, see below. - -<sect3>RENDER (supported) - -<p>The X Rendering Extension (RENDER) provides support for digital image -composition. Geometric and text rendering are supported. RENDER is -partially Xinerama-aware, with text and the most basic compositing -operator; however, its higher level primitives (triangles, triangle -strips, and triangle fans) are not yet Xinerama-aware. The RENDER -extension is still under development, and is currently at version 0.8. -Additional support will be required in DMX as more primitives and/or -requests are added to the extension. - -<p>There is currently no test suite for the X Rendering Extension; -however, there has been discussion of developing a test suite as the -extension matures. When that test suite becomes available, additional -testing can be performed with Xdmx. The X Test Suite passed and failed -the exact same tests before and after this extension was enabled. - -<sect3>Summary - -<!-- WARNING: this list is duplicated in the "Common X extension -support" section --> -<p>To summarize, the following extensions are currently supported: - BIG-REQUESTS, - DEC-XTRAP, - DMX, - DPMS, - Extended-Visual-Information, - GLX, - LBX, - RECORD, - RENDER, - SECURITY, - SHAPE, - SYNC, - X-Resource, - XC-APPGROUP, - XC-MISC, - XFree86-Bigfont, - XINERAMA, - XInputExtension, - XKEYBOARD, and - XTEST. - -<p>The following extensions are <em/not/ supported at this time: - DOUBLE-BUFFER, - FontCache, - MIT-SCREEN-SAVER, - MIT-SHM, - MIT-SUNDRY-NONSTANDARD, - TOG-CUP, - XFree86-DGA, - XFree86-Misc, - XFree86-VidModeExtension, - XTestExtensionExt1, and - XVideo. - -<sect2>Additional Testing with the X Test Suite - -<sect3>XFree86 without XTEST - -<p>After the release of XFree86 4.3.0, we retested the XFree86 X server -with and without using the XTEST extension. When the XTEST extension -was <em/not/ used for testing, the XFree86 4.3.0 server running on our -usual test system with a Radeon VE card reported unexpected failures in -the following tests: -<verb> -XListPixmapFormats: Test 1 -XChangeKeyboardControl: Tests 9, 10 -XGetDefault: Test 5 -XRebindKeysym: Test 1 -</verb> - -<sect3>XFree86 with XTEST - -<p>When using the XTEST extension, the XFree86 4.3.0 server reported the -following errors: -<verb> -XListPixmapFormats: Test 1 -XChangeKeyboardControl: Tests 9, 10 -XGetDefault: Test 5 -XRebindKeysym: Test 1 - -XAllowEvents: Tests 20, 21, 24 -XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 -XGrabKey: Test 8 -XSetPointerMapping: Test 3 -XUngrabButton: Test 4 -</verb> - -<p>While these errors may be important, they will probably be fixed -eventually in the XFree86 source tree. We are particularly interested -in demonstrating that the Xdmx server does not introduce additional -failures that are not known Xinerama failures. - -<sect3>Xdmx with XTEST, without Xinerama, without GLX - -<p>Without Xinerama, but using the XTEST extension, the following errors -were reported from Xdmx (note that these are the same as for the XFree86 -4.3.0, except that XGetDefault no longer fails): -<verb> -XListPixmapFormats: Test 1 -XChangeKeyboardControl: Tests 9, 10 -XRebindKeysym: Test 1 - -XAllowEvents: Tests 20, 21, 24 -XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 -XGrabKey: Test 8 -XSetPointerMapping: Test 3 -XUngrabButton: Test 4 -</verb> - -<sect3>Xdmx with XTEST, with Xinerama, without GLX - -<p>With Xinerama, using the XTEST extension, the following errors -were reported from Xdmx: -<verb> -XListPixmapFormats: Test 1 -XChangeKeyboardControl: Tests 9, 10 -XRebindKeysym: Test 1 - -XAllowEvents: Tests 20, 21, 24 -XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 -XGrabKey: Test 8 -XSetPointerMapping: Test 3 -XUngrabButton: Test 4 - -XCopyPlane: Tests 13, 22, 31 (well-known XTEST/Xinerama interaction issue) -XDrawLine: Test 67 -XDrawLines: Test 91 -XDrawSegments: Test 68 -</verb> -Note that the first two sets of errors are the same as for the XFree86 -4.3.0 server, and that the XCopyPlane error is a well-known error -resulting from an XTEST/Xinerama interaction when the request crosses a -screen boundary. The XDraw* errors are resolved when the tests are run -individually and they do not cross a screen boundary. We will -investigate these errors further to determine their cause. - -<sect3>Xdmx with XTEST, with Xinerama, with GLX - -<p>With GLX enabled, using the XTEST extension, the following errors -were reported from Xdmx (these results are from early during the Phase -IV development, but were confirmed with a late Phase IV snapshot): -<verb> -XListPixmapFormats: Test 1 -XChangeKeyboardControl: Tests 9, 10 -XRebindKeysym: Test 1 - -XAllowEvents: Tests 20, 21, 24 -XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 -XGrabKey: Test 8 -XSetPointerMapping: Test 3 -XUngrabButton: Test 4 - -XClearArea: Test 8 -XCopyArea: Tests 4, 5, 11, 14, 17, 23, 25, 27, 30 -XCopyPlane: Tests 6, 7, 10, 19, 22, 31 -XDrawArcs: Tests 89, 100, 102 -XDrawLine: Test 67 -XDrawSegments: Test 68 -</verb> -Note that the first two sets of errors are the same as for the XFree86 -4.3.0 server, and that the third set has different failures than when -Xdmx does not include GLX support. Since the GLX extension adds new -visuals to support GLX's visual configs and the X Test Suite runs tests -over the entire set of visuals, additional rendering tests were run and -presumably more of them crossed a screen boundary. This conclusion is -supported by the fact that nearly all of the rendering errors reported -are resolved when the tests are run individually and they do no cross a -screen boundary. - -<p>Further, when hardware rendering is disabled on the back-end displays, -many of the errors in the third set are eliminated, leaving only: -<verb> -XClearArea: Test 8 -XCopyArea: Test 4, 5, 11, 14, 17, 23, 25, 27, 30 -XCopyPlane: Test 6, 7, 10, 19, 22, 31 -</verb> - -<sect3>Conclusion - -<p>We conclude that all of the X Test Suite errors reported for Xdmx are -the result of errors in the back-end X server or the Xinerama -implementation. Further, all of these errors that can be reasonably -fixed at the Xdmx layer have been. (Where appropriate, we have -submitted patches to the XFree86 and Xinerama upstream maintainers.) - -<sect2>Dynamic Reconfiguration - -<p>During this development phase, dynamic reconfiguration support was -added to DMX. This support allows an application to change the position -and offset of a back-end server's screen. For example, if the -application would like to shift a screen slightly to the left, it could -query Xdmx for the screen's <x,y> position and then dynamically -reconfigure that screen to be at position <x+10,y>. When a screen -is dynamically reconfigured, input handling and a screen's root window -dimensions are adjusted as needed. These adjustments are transparent to -the user. - -<sect3>Dynamic reconfiguration extension - -<p>The application interface to DMX's dynamic reconfiguration is through -a function in the DMX extension library: -<verb> -Bool DMXReconfigureScreen(Display *dpy, int screen, int x, int y) -</verb> -where <it/dpy/ is DMX server's display, <it/screen/ is the number of the -screen to be reconfigured, and <it/x/ and <it/y/ are the new upper, -left-hand coordinates of the screen to be reconfigured. - -<p>The coordinates are not limited other than as required by the X -protocol, which limits all coordinates to a signed 16 bit number. In -addition, all coordinates within a screen must also be legal values. -Therefore, setting a screen's upper, left-hand coordinates such that the -right or bottom edges of the screen is greater than 32,767 is illegal. - -<sect3>Bounding box - -<p>When the Xdmx server is started, a bounding box is calculated from -the screens' layout given either on the command line or in the -configuration file. This bounding box is currently fixed for the -lifetime of the Xdmx server. - -<p>While it is possible to move a screen outside of the bounding box, it -is currently not possible to change the dimensions of the bounding box. -For example, it is possible to specify coordinates of <-100,-100> -for the upper, left-hand corner of the bounding box, which was -previously at coordinates <0,0>. As expected, the screen is moved -down and to the right; however, since the bounding box is fixed, the -left side and upper portions of the screen exposed by the -reconfiguration are no longer accessible on that screen. Those -inaccessible regions are filled with black. - -<p>This fixed bounding box limitation will be addressed in a future -development phase. - -<sect3>Sample applications - -<p>An example of where this extension is useful is in setting up a video -wall. It is not always possible to get everything perfectly aligned, -and sometimes the positions are changed (e.g., someone might bump into a -projector). Instead of physically moving projectors or monitors, it is -now possible to adjust the positions of the back-end server's screens -using the dynamic reconfiguration support in DMX. - -<p>Other applications, such as automatic setup and calibration tools, -can make use of dynamic reconfiguration to correct for projector -alignment problems, as long as the projectors are still arranged -rectilinearly. Horizontal and vertical keystone correction could be -applied to projectors to correct for non-rectilinear alignment problems; -however, this must be done external to Xdmx. - -<p>A sample test program is included in the DMX server's examples -directory to demonstrate the interface and how an application might use -dynamic reconfiguration. See <tt/dmxreconfig.c/ for details. - -<sect3>Additional notes - -<p>In the original development plan, Phase IV was primarily devoted to -adding OpenGL support to DMX; however, SGI became interested in the DMX -project and developed code to support OpenGL/GLX. This code was later -donated to the DMX project and integrated into the DMX code base, which -freed the DMX developers to concentrate on dynamic reconfiguration (as -described above). - -<sect2>Doxygen documentation - -<p>Doxygen is an open-source (GPL) documentation system for generating -browseable documentation from stylized comments in the source code. We -have placed all of the Xdmx server and DMX protocol source code files -under Doxygen so that comprehensive documentation for the Xdmx source -code is available in an easily browseable format. - -<sect2>Valgrind - -<p>Valgrind, an open-source (GPL) memory debugger for Linux, was used to -search for memory management errors. Several memory leaks were detected -and repaired. The following errors were not addressed: -<enum> - <item> - When the X11 transport layer sends a reply to the client, only - those fields that are required by the protocol are filled in -- - unused fields are left as uninitialized memory and are therefore - noted by valgrind. These instances are not errors and were not - repaired. - <item> - At each server generation, glxInitVisuals allocates memory that - is never freed. The amount of memory lost each generation - approximately equal to 128 bytes for each back-end visual. - Because the code involved is automatically generated, this bug - has not been fixed and will be referred to SGI. - <item> - At each server generation, dmxRealizeFont calls XLoadQueryFont, - which allocates a font structure that is not freed. - dmxUnrealizeFont can free the font structure for the first - screen, but cannot free it for the other screens since they are - already closed by the time dmxUnrealizeFont could free them. - The amount of memory lost each generation is approximately equal - to 80 bytes per font per back-end. When this bug is fixed in - the the X server's device-independent (dix) code, DMX will be - able to properly free the memory allocated by XLoadQueryFont. -</enum> - -<sect2>RATS - -<p>RATS (Rough Auditing Tool for Security) is an open-source (GPL) -security analysis tool that scans source code for common -security-related programming errors (e.g., buffer overflows and TOCTOU -races). RATS was used to audit all of the code in the hw/dmx directory -and all "High" notations were checked manually. The code was either -re-written to eliminate the warning, or a comment containing "RATS" was -inserted on the line to indicate that a human had checked the code. -Unrepaired warnings are as follows: -<enum> - <item> - Fixed-size buffers are used in many areas, but code has been - added to protect against buffer overflows (e.g., XmuSnprint). - The only instances that have not yet been fixed are in - config/xdmxconfig.c (which is not part of the Xdmx server) and - input/usb-common.c. - <item> - vprintf and vfprintf are used in the logging routines. In - general, all uses of these functions (e.g., dmxLog) provide a - constant format string from a trusted source, so the use is - relatively benign. - <item> - glxProxy/glxscreens.c uses getenv and strcat. The use of these - functions is safe and will remain safe as long as - ExtensionsString is longer then GLXServerExtensions (ensuring - this may not be ovious to the casual programmer, but this is in - automatically generated code, so we hope that the generator - enforces this constraint). -</enum> - - </article> - - <!-- Local Variables: --> - <!-- fill-column: 72 --> - <!-- End: --> diff --git a/xorg-server/hw/dmx/doc/dmx.xml b/xorg-server/hw/dmx/doc/dmx.xml new file mode 100644 index 000000000..06716d1d7 --- /dev/null +++ b/xorg-server/hw/dmx/doc/dmx.xml @@ -0,0 +1,3447 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" + "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [ +]> + +<article> + + <articleinfo> + <!-- Title information --> + <title>Distributed Multihead X design + + Kevin E.Martin + David H.Dawes + Rickard E.Faith + + 29 June 2004 (created 25 July 2001) + + This document covers the motivation, background, design, and + implementation of the distributed multihead X (DMX) system. It + is a living document and describes the current design and + implementation details of the DMX system. As the project + progresses, this document will be continually updated to reflect + the changes in the code and/or design. Copyright 2001 by VA + Linux Systems, Inc., Fremont, California. Copyright 2001-2004 + by Red Hat, Inc., Raleigh, North Carolina + + + + + +Introduction + + +The Distributed Multihead X Server + +Current Open Source multihead solutions are limited to a single +physical machine. A single X server controls multiple display devices, +which can be arranged as independent heads or unified into a single +desktop (with Xinerama). These solutions are limited to the number of +physical devices that can co-exist in a single machine (e.g., due to the +number of AGP/PCI slots available for graphics cards). Thus, large +tiled displays are not currently possible. The work described in this +paper will eliminate the requirement that the display devices reside in +the same physical machine. This will be accomplished by developing a +front-end proxy X server that will control multiple back-end X servers +that make up the large display. + + +The overall structure of the distributed multihead X (DMX) project is +as follows: A single front-end X server will act as a proxy to a set of +back-end X servers, which handle all of the visible rendering. X +clients will connect to the front-end server just as they normally would +to a regular X server. The front-end server will present an abstracted +view to the client of a single large display. This will ensure that all +standard X clients will continue to operate without modification +(limited, as always, by the visuals and extensions provided by the X +server). Clients that are DMX-aware will be able to use an extension to +obtain information about the back-end servers (e.g., for placement of +pop-up windows, window alignments by the window manager, etc.). + + +The architecture of the DMX server is divided into two main sections: +input (e.g., mouse and keyboard events) and output (e.g., rendering and +windowing requests). Each of these are describe briefly below, and the +rest of this design document will describe them in greater detail. + + +The DMX server can receive input from three general types of input +devices: "local" devices that are physically attached to the machine on +which DMX is running, "backend" devices that are physically attached to +one or more of the back-end X servers (and that generate events via the +X protocol stream from the backend), and "console" devices that can be +abstracted from any non-back-end X server. Backend and console devices +are treated differently because the pointer device on the back-end X +server also controls the location of the hardware X cursor. Full +support for XInput extension devices is provided. + + +Rendering requests will be accepted by the front-end server; however, +rendering to visible windows will be broken down as needed and sent to +the appropriate back-end server(s) via X11 library calls for actual +rendering. The basic framework will follow a Xnest-style approach. GC +state will be managed in the front-end server and sent to the +appropriate back-end server(s) as required. Pixmap rendering will (at +least initially) be handled by the front-end X server. Windowing +requests (e.g., ordering, mapping, moving, etc.) will handled in the +front-end server. If the request requires a visible change, the +windowing operation will be translated into requests for the appropriate +back-end server(s). Window state will be mirrored in the back-end +server(s) as needed. + + + + +Layout of Paper + +The next section describes the general development plan that was +actually used for implementation. The final section discusses +outstanding issues at the conclusion of development. The first appendix +provides low-level technical detail that may be of interest to those +intimately familiar with the X server architecture. The final appendix +describes the four phases of development that were performed during the +first two years of development. + + +The final year of work was divided into 9 tasks that are not +described in specific sections of this document. The major tasks during +that time were the enhancement of the reconfiguration ability added in +Phase IV, addition of support for a dynamic number of back-end displays +(instead of a hard-coded limit), and the support for back-end display +and input removal and addition. This work is mentioned in this paper, +but is not covered in detail. + + + + + + +Development plan + +This section describes the development plan from approximately June +2001 through July 2003. + + + +Bootstrap code + +To allow for rapid development of the DMX server by multiple +developers during the first development stage, the problem will be +broken down into three tasks: the overall DMX framework, back-end +rendering services and input device handling services. However, before +the work begins on these tasks, a simple framework that each developer +could use was implemented to bootstrap the development effort. This +framework renders to a single back-end server and provides dummy input +devices (i.e., the keyboard and mouse). The simple back-end rendering +service was implemented using the shadow framebuffer support currently +available in the XFree86 environment. + + +Using this bootstrapping framework, each developer has been able to +work on each of the tasks listed above independently as follows: the +framework will be extended to handle arbitrary back-end server +configurations; the back-end rendering services will be transitioned to +the more efficient Xnest-style implementation; and, an input device +framework to handle various input devices via the input extension will +be developed. + + +Status: The boot strap code is complete. + + + + + +Input device handling + +An X server (including the front-end X server) requires two core +input devices -- a keyboard and a pointer (mouse). These core devices +are handled and required by the core X11 protocol. Additional types of +input devices may be attached and utilized via the XInput extension. +These are usually referred to as ``XInput extension devices'', + + +There are some options as to how the front-end X server gets its core +input devices: + + + + Local Input. The physical input devices (e.g., keyboard and + mouse) can be attached directly to the front-end X server. In this + case, the keyboard and mouse on the machine running the front-end X + server will be used. The front-end will have drivers to read the + raw input from those devices and convert it into the required X + input events (e.g., key press/release, pointer button press/release, + pointer motion). The front-end keyboard driver will keep track of + keyboard properties such as key and modifier mappings, autorepeat + state, keyboard sound and led state. Similarly the front-end + pointer driver will keep track if pointer properties such as the + button mapping and movement acceleration parameters. With this + option, input is handled fully in the front-end X server, and the + back-end X servers are used in a display-only mode. This option was + implemented and works for a limited number of Linux-specific + devices. Adding additional local input devices for other + architectures is expected to be relatively simple. + + + The following options are available for implementing local input + devices: + + + + The XFree86 X server has modular input drivers that could + be adapted for this purpose. The mouse driver supports a wide + range of mouse types and interfaces, as well as a range of + Operating System platforms. The keyboard driver in XFree86 is + not currently as modular as the mouse driver, but could be made + so. The XFree86 X server also has a range of other input + drivers for extended input devices such as tablets and touch + screens. Unfortunately, the XFree86 drivers are generally + complex, often simultaneously providing support for multiple + devices across multiple architectures; and rely so heavily on + XFree86-specific helper-functions, that this option was not + pursued. + + + + + The kdrive X server in XFree86 has built-in drivers that + support PS/2 mice and keyboard under Linux. The mouse driver + can indirectly handle other mouse types if the Linux utility + gpm is used as to translate the native mouse protocol into + PS/2 mouse format. These drivers could be adapted and built in + to the front-end X server if this range of hardware and OS + support is sufficient. While much simpler than the XFree86 + drivers, the kdrive drivers were not used for the DMX + implementation. + + + + + Reimplementation of keyboard and mouse drivers from + scratch for the DMX framework. Because keyboard and mouse + drivers are relatively trivial to implement, this pathway was + selected. Other drivers in the X source tree were referenced, + and significant contributions from other drivers are noted in + the DMX source code. + + + + + + + + Backend Input. The front-end can make use of the core input + devices attached to one or more of the back-end X servers. Core + input events from multiple back-ends are merged into a single input + event stream. This can work sanely when only a single set of input + devices is used at any given time. The keyboard and pointer state + will be handled in the front-end, with changes propagated to the + back-end servers as needed. This option was implemented and works + well. Because the core pointer on a back-end controls the hardware + mouse on that back-end, core pointers cannot be treated as XInput + extension devices. However, all back-end XInput extensions devices + can be mapped to either DMX core or DMX XInput extension devices. + + + + + Console Input. The front-end server could create a console + window that is displayed on an X server independent of the back-end + X servers. This console window could display things like the + physical screen layout, and the front-end could get its core input + events from events delivered to the console window. This option was + implemented and works well. To help the human navigate, window + outlines are also displayed in the console window. Further, console + windows can be used as either core or XInput extension devices. + + + + + Other options were initially explored, but they were all + partial subsets of the options listed above and, hence, are + irrelevant. + + + + + + +Although extended input devices are not specifically mentioned in the +Distributed X requirements, the options above were all implemented so +that XInput extension devices were supported. + + +The bootstrap code (Xdmx) had dummy input devices, and these are +still supported in the final version. These do the necessary +initialization to satisfy the X server's requirements for core pointer +and keyboard devices, but no input events are ever generated. + + +Status: The input code is complete. Because of the complexity of the +XFree86 input device drivers (and their heavy reliance on XFree86 +infrastructure), separate low-level device drivers were implemented for +Xdmx. The following kinds of drivers are supported (in general, the +devices can be treated arbitrarily as "core" input devices or as XInput +"extension" devices; and multiple instances of different kinds of +devices can be simultaneously available): + + + A "dummy" device drive that never generates events. + + + + + "Local" input is from the low-level hardware on which the + Xdmx binary is running. This is the only area where using the + XFree86 driver infrastructure would have been helpful, and then + only partially, since good support for generic USB devices does + not yet exist in XFree86 (in any case, XFree86 and kdrive driver + code was used where possible). Currently, the following local + devices are supported under Linux (porting to other operating + systems should be fairly straightforward): + + Linux keyboard + Linux serial mouse (MS) + Linux PS/2 mouse + USB keyboard + USB mouse + USB generic device (e.g., joystick, gamepad, etc.) + + + + + + "Backend" input is taken from one or more of the back-end + displays. In this case, events are taken from the back-end X + server and are converted to Xdmx events. Care must be taken so + that the sprite moves properly on the display from which input + is being taken. + + + + + "Console" input is taken from an X window that Xdmx + creates on the operator's display (i.e., on the machine running + the Xdmx binary). When the operator's mouse is inside the + console window, then those events are converted to Xdmx events. + Several special features are available: the console can display + outlines of windows that are on the Xdmx display (to facilitate + navigation), the cursor can be confined to the console, and a + "fine" mode can be activated to allow very precise cursor + positioning. + + + + + + + + + + + +Output device handling + +The output of the DMX system displays rendering and windowing +requests across multiple screens. The screens are typically arranged in +a grid such that together they represent a single large display. + + +The output section of the DMX code consists of two parts. The first +is in the front-end proxy X server (Xdmx), which accepts client +connections, manages the windows, and potentially renders primitives but +does not actually display any of the drawing primitives. The second +part is the back-end X server(s), which accept commands from the +front-end server and display the results on their screens. + + + +Initialization + +The DMX front-end must first initialize its screens by connecting to +each of the back-end X servers and collecting information about each of +these screens. However, the information collected from the back-end X +servers might be inconsistent. Handling these cases can be difficult +and/or inefficient. For example, a two screen system has one back-end X +server running at 16bpp while the second is running at 32bpp. +Converting rendering requests (e.g., XPutImage() or XGetImage() +requests) to the appropriate bit depth can be very time consuming. +Analyzing these cases to determine how or even if it is possible to +handle them is required. The current Xinerama code handles many of +these cases (e.g., in PanoramiXConsolidate()) and will be used as a +starting point. In general, the best solution is to use homogeneous X +servers and display devices. Using back-end servers with the same depth +is a requirement of the final DMX implementation. + + +Once this screen consolidation is finished, the relative position of +each back-end X server's screen in the unified screen is initialized. A +full-screen window is opened on each of the back-end X servers, and the +cursor on each screen is turned off. The final DMX implementation can +also make use of a partial-screen window, or multiple windows per +back-end screen. + + + + +Handling rendering requests + +After initialization, X applications connect to the front-end server. +There are two possible implementations of how rendering and windowing +requests are handled in the DMX system: + + + + A shadow framebuffer is used in the front-end server as the + render target. In this option, all protocol requests are completely + handled in the front-end server. All state and resources are + maintained in the front-end including a shadow copy of the entire + framebuffer. The framebuffers attached to the back-end servers are + updated by XPutImage() calls with data taken directly from the + shadow framebuffer. + + + This solution suffers from two main problems. First, it does not + take advantage of any accelerated hardware available in the system. + Second, the size of the XPutImage() calls can be quite large and + thus will be limited by the bandwidth available. + + + The initial DMX implementation used a shadow framebuffer by + default. + + + + + Rendering requests are sent to each back-end server for + handling (as is done in the Xnest server described above). In this + option, certain protocol requests are handled in the front-end + server and certain requests are repackaged and then sent to the + back-end servers. The framebuffer is distributed across the + multiple back-end servers. Rendering to the framebuffer is handled + on each back-end and can take advantage of any acceleration + available on the back-end servers' graphics display device. State + is maintained both in the front and back-end servers. + + + This solution suffers from two main drawbacks. First, protocol + requests are sent to all back-end servers -- even those that will + completely clip the rendering primitive -- which wastes bandwidth + and processing time. Second, state is maintained both in the front- + and back-end servers. These drawbacks are not as severe as in + option 1 (above) and can either be overcome through optimizations or + are acceptable. Therefore, this option will be used in the final + implementation. + + + The final DMX implementation defaults to this mechanism, but also + supports the shadow framebuffer mechanism. Several optimizations + were implemented to eliminate the drawbacks of the default + mechanism. These optimizations are described the section below and + in Phase II of the Development Results (see appendix). + + + + + + +Status: Both the shadow framebuffer and Xnest-style code is complete. + + + + + + + +Optimizing DMX + +Initially, the Xnest-style solution's performance will be measured +and analyzed to determine where the performance bottlenecks exist. +There are four main areas that will be addressed. + + +First, to obtain reasonable interactivity with the first development +phase, XSync() was called after each protocol request. The XSync() +function flushes any pending protocol requests. It then waits for the +back-end to process the request and send a reply that the request has +completed. This happens with each back-end server and performance +greatly suffers. As a result of the way XSync() is called in the first +development phase, the batching that the X11 library performs is +effectively defeated. The XSync() call usage will be analyzed and +optimized by batching calls and performing them at regular intervals, +except where interactivity will suffer (e.g., on cursor movements). + + +Second, the initial Xnest-style solution described above sends the +repackaged protocol requests to all back-end servers regardless of +whether or not they would be completely clipped out. The requests that +are trivially rejected on the back-end server wastes the limited +bandwidth available. By tracking clipping changes in the DMX X server's +windowing code (e.g., by opening, closing, moving or resizing windows), +we can determine whether or not back-end windows are visible so that +trivial tests in the front-end server's GC ops drawing functions can +eliminate these unnecessary protocol requests. + + +Third, each protocol request will be analyzed to determine if it is +possible to break the request into smaller pieces at display boundaries. +The initial ones to be analyzed are put and get image requests since +they will require the greatest bandwidth to transmit data between the +front and back-end servers. Other protocol requests will be analyzed +and those that will benefit from breaking them into smaller requests +will be implemented. + + +Fourth, an extension is being considered that will allow font glyphs to +be transferred from the front-end DMX X server to each back-end server. +This extension will permit the front-end to handle all font requests and +eliminate the requirement that all back-end X servers share the exact +same fonts as the front-end server. We are investigating the +feasibility of this extension during this development phase. + + +Other potential optimizations will be determined from the performance +analysis. + + +Please note that in our initial design, we proposed optimizing BLT +operations (e.g., XCopyArea() and window moves) by developing an +extension that would allow individual back-end servers to directly copy +pixel data to other back-end servers. This potential optimization was +in response to the simple image movement implementation that required +potentially many calls to GetImage() and PutImage(). However, the +current Xinerama implementation handles these BLT operations +differently. Instead of copying data to and from screens, they generate +expose events -- just as happens in the case when a window is moved from +off a screen to on screen. This approach saves the limited bandwidth +available between front and back-end servers and is being standardized +with Xinerama. It also eliminates the potential setup problems and +security issues resulting from having each back-end server open +connections to all other back-end servers. Therefore, we suggest +accepting Xinerama's expose event solution. + + +Also note that the approach proposed in the second and third +optimizations might cause backing store algorithms in the back-end to be +defeated, so a DMX X server configuration flag will be added to disable +these optimizations. + + +Status: The optimizations proposed above are complete. It was +determined that the using the xfs font server was sufficient and +creating a new mechanism to pass glyphs was redundant; therefore, the +fourth optimization proposed above was not included in DMX. + + + + + + +DMX X extension support + +The DMX X server keeps track of all the windowing information on the +back-end X servers, but does not currently export this information to +any client applications. An extension will be developed to pass the +screen information and back-end window IDs to DMX-aware clients. These +clients can then use this information to directly connect to and render +to the back-end windows. Bypassing the DMX X server allows DMX-aware +clients to break up complex rendering requests on their own and send +them directly to the windows on the back-end server's screens. An +example of a client that can make effective use of this extension is +Chromium. + + +Status: The extension, as implemented, is fully documented in +"Client-to-Server DMX Extension to the X Protocol". Future changes +might be required based on feedback and other proposed enhancements to +DMX. Currently, the following facilities are supported: + + + Screen information (clipping rectangle for each screen relative + to the virtual screen) + + + Window information (window IDs and clipping information for each + back-end window that corresponds to each DMX window) + + + Input device information (mappings from DMX device IDs to + back-end device IDs) + + + Force window creation (so that a client can override the + server-side lazy window creation optimization) + + + Reconfiguration (so that a client can request that a screen + position be changed) + + + Addition and removal of back-end servers and back-end and + console inputs. + + + + + + + + +Common X extension support + +The XInput, XKeyboard and Shape extensions are commonly used +extensions to the base X11 protocol. XInput allows multiple and +non-standard input devices to be accessed simultaneously. These input +devices can be connected to either the front-end or back-end servers. +XKeyboard allows much better keyboard mappings control. Shape adds +support for arbitrarily shaped windows and is used by various window +managers. Nearly all potential back-end X servers make these extensions +available, and support for each one will be added to the DMX system. + + +In addition to the extensions listed above, support for the X +Rendering extension (Render) is being developed. Render adds digital +image composition to the rendering model used by the X Window System. +While this extension is still under development by Keith Packard of HP, +support for the current version will be added to the DMX system. + + +Support for the XTest extension was added during the first +development phase. + + + +Status: The following extensions are supported and are discussed in +more detail in Phase IV of the Development Results (see appendix): + BIG-REQUESTS, + DEC-XTRAP, + DMX, + DPMS, + Extended-Visual-Information, + GLX, + LBX, + RECORD, + RENDER, + SECURITY, + SHAPE, + SYNC, + X-Resource, + XC-APPGROUP, + XC-MISC, + XFree86-Bigfont, + XINERAMA, + XInputExtension, + XKEYBOARD, and + XTEST. + + + + + +OpenGL support + +OpenGL support using the Mesa code base exists in XFree86 release 4 +and later. Currently, the direct rendering infrastructure (DRI) +provides accelerated OpenGL support for local clients and unaccelerated +OpenGL support (i.e., software rendering) is provided for non-local +clients. + + +The single head OpenGL support in XFree86 4.x will be extended to use +the DMX system. When the front and back-end servers are on the same +physical hardware, it is possible to use the DRI to directly render to +the back-end servers. First, the existing DRI will be extended to +support multiple display heads, and then to support the DMX system. +OpenGL rendering requests will be direct rendering to each back-end X +server. The DRI will request the screen layout (either from the +existing Xinerama extension or a DMX-specific extension). Support for +synchronized swap buffers will also be added (on hardware that supports +it). Note that a single front-end server with a single back-end server +on the same physical machine can emulate accelerated indirect rendering. + + +When the front and back-end servers are on different physical +hardware or are using non-XFree86 4.x X servers, a mechanism to render +primitives across the back-end servers will be provided. There are +several options as to how this can be implemented. + + + + + The existing OpenGL support in each back-end server can be + used by repackaging rendering primitives and sending them to each + back-end server. This option is similar to the unoptimized + Xnest-style approach mentioned above. Optimization of this solution + is beyond the scope of this project and is better suited to other + distributed rendering systems. + + + + Rendering to a pixmap in the front-end server using the + current XFree86 4.x code, and then displaying to the back-ends via + calls to XPutImage() is another option. This option is similar to + the shadow frame buffer approach mentioned above. It is slower and + bandwidth intensive, but has the advantage that the back-end servers + are not required to have OpenGL support. + + + +These, and other, options will be investigated in this phase of the +work. + + +Work by others have made Chromium DMX-aware. Chromium will use the +DMX X protocol extension to obtain information about the back-end +servers and will render directly to those servers, bypassing DMX. + + +Status: OpenGL support by the glxProxy extension was implemented by +SGI and has been integrated into the DMX code base. + + + + + + + + +Current issues + +In this sections the current issues are outlined that require further +investigation. + + + +Fonts + +The font path and glyphs need to be the same for the front-end and +each of the back-end servers. Font glyphs could be sent to the back-end +servers as necessary but this would consume a significant amount of +available bandwidth during font rendering for clients that use many +different fonts (e.g., Netscape). Initially, the font server (xfs) will +be used to provide the fonts to both the front-end and back-end servers. +Other possibilities will be investigated during development. + + + + +Zero width rendering primitives + +To allow pixmap and on-screen rendering to be pixel perfect, all +back-end servers must render zero width primitives exactly the same as +the front-end renders the primitives to pixmaps. For those back-end +servers that do not exactly match, zero width primitives will be +automatically converted to one width primitives. This can be handled in +the front-end server via the GC state. + + + + +Output scaling + +With very large tiled displays, it might be difficult to read the +information on the standard X desktop. In particular, the cursor can be +easily lost and fonts could be difficult to read. Automatic primitive +scaling might prove to be very useful. We will investigate the +possibility of scaling the cursor and providing a set of alternate +pre-scaled fonts to replace the standard fonts that many applications +use (e.g., fixed). Other options for automatic scaling will also be +investigated. + + + + +Per-screen colormaps + +Each screen's default colormap in the set of back-end X servers +should be able to be adjusted via a configuration utility. This support +is would allow the back-end screens to be calibrated via custom gamma +tables. On 24-bit systems that support a DirectColor visual, this type +of correction can be accommodated. One possible implementation would be +to advertise to X client of the DMX server a TrueColor visual while +using DirectColor visuals on the back-end servers to implement this type +of color correction. Other options will be investigated. + + + + + + +Appendix + + +Background + +This section describes the existing Open Source architectures that +can be used to handle multiple screens and upon which this development +project is based. This section was written before the implementation +was finished, and may not reflect actual details of the implementation. +It is left for historical interest only. + + + +Core input device handling + +The following is a description of how core input devices are handled +by an X server. + + + +InitInput() + +InitInput() is a DDX function that is called at the start of each +server generation from the X server's main() function. Its purpose is +to determine what input devices are connected to the X server, register +them with the DIX and MI layers, and initialize the input event queue. +InitInput() does not have a return value, but the X server will abort if +either a core keyboard device or a core pointer device are not +registered. Extended input (XInput) devices can also be registered in +InitInput(). + + +InitInput() usually has implementation specific code to determine +which input devices are available. For each input device it will be +using, it calls AddInputDevice(): + + + +AddInputDevice() +This DIX function allocates the device structure, +registers a callback function (which handles device init, close, on and +off), and returns the input handle, which can be treated as opaque. It +is called once for each input device. + + + + + +Once input handles for core keyboard and core pointer devices have +been obtained from AddInputDevice(), they are registered as core devices +by calling RegisterPointerDevice() and RegisterKeyboardDevice(). Each +of these should be called once. If both core devices are not +registered, then the X server will exit with a fatal error when it +attempts to start the input devices in InitAndStartDevices(), which is +called directly after InitInput() (see below). + + + +Register{Pointer,Keyboard}Device() +These DIX functions take a +handle returned from AddInputDevice() and initialize the core input +device fields in inputInfo, and initialize the input processing and grab +functions for each core input device. + + + + +The core pointer device is then registered with the miPointer code +(which does the high level cursor handling). While this registration +is not necessary for correct miPointer operation in the current XFree86 +code, it is still done mostly for compatibility reasons. + + + + + +miRegisterPointerDevice() +This MI function registers the core +pointer's input handle with with the miPointer code. + + + + +The final part of InitInput() is the initialization of the input +event queue handling. In most cases, the event queue handling provided +in the MI layer is used. The primary XFree86 X server uses its own +event queue handling to support some special cases related to the XInput +extension and the XFree86-specific DGA extension. For our purposes, the +MI event queue handling should be suitable. It is initialized by +calling mieqInit(): + + + +mieqInit() +This MI function initializes the MI event queue for the +core devices, and is passed the public component of the input handles +for the two core devices. + + + + +If a wakeup handler is required to deliver synchronous input +events, it can be registered here by calling the DIX function +RegisterBlockAndWakeupHandlers(). (See the devReadInput() description +below.) + + + + +InitAndStartDevices() + +InitAndStartDevices() is a DIX function that is called immediately +after InitInput() from the X server's main() function. Its purpose is +to initialize each input device that was registered with +AddInputDevice(), enable each input device that was successfully +initialized, and create the list of enabled input devices. Once each +registered device is processed in this way, the list of enabled input +devices is checked to make sure that both a core keyboard device and +core pointer device were registered and successfully enabled. If not, +InitAndStartDevices() returns failure, and results in the the X server +exiting with a fatal error. + + +Each registered device is initialized by calling its callback +(dev->deviceProc) with the DEVICE_INIT argument: + + + +(*dev->deviceProc)(dev, DEVICE_INIT) + +This function initializes the +device structs with core information relevant to the device. + + +For pointer devices, this means specifying the number of buttons, +default button mapping, the function used to get motion events (usually +miPointerGetMotionEvents()), the function used to change/control the +core pointer motion parameters (acceleration and threshold), and the +motion buffer size. + + +For keyboard devices, this means specifying the keycode range, +default keycode to keysym mapping, default modifier mapping, and the +functions used to sound the keyboard bell and modify/control the +keyboard parameters (LEDs, bell pitch and duration, key click, which +keys are auto-repeating, etc). + + + + +Each initialized device is enabled by calling EnableDevice(): + + + +EnableDevice() + +EnableDevice() calls the device callback with +DEVICE_ON: + + + (*dev->deviceProc)(dev, DEVICE_ON) + + This typically opens and + initializes the relevant physical device, and when appropriate, + registers the device's file descriptor (or equivalent) as a valid + input source. + + + + + EnableDevice() then adds the device handle to the X server's + global list of enabled devices. + + + + +InitAndStartDevices() then verifies that a valid core keyboard and +pointer has been initialized and enabled. It returns failure if either +are missing. + + + + +devReadInput() + +Each device will have some function that gets called to read its +physical input. These may be called in a number of different ways. In +the case of synchronous I/O, they will be called from a DDX +wakeup-handler that gets called after the server detects that new input is +available. In the case of asynchronous I/O, they will be called from a +(SIGIO) signal handler triggered when new input is available. This +function should do at least two things: make sure that input events get +enqueued, and make sure that the cursor gets moved for motion events +(except if these are handled later by the driver's own event queue +processing function, which cannot be done when using the MI event queue +handling). + + +Events are queued by calling mieqEnqueue(): + + + +mieqEnqueue() + +This MI function is used to add input events to the +event queue. It is simply passed the event to be queued. + + + + +The cursor position should be updated when motion events are +enqueued, by calling either miPointerAbsoluteCursor() or +miPointerDeltaCursor(): + + + +miPointerAbsoluteCursor() + +This MI function is used to move the +cursor to the absolute coordinates provided. + + +miPointerDeltaCursor() + +This MI function is used to move the cursor +relative to its current position. + + + + + + +ProcessInputEvents() + +ProcessInputEvents() is a DDX function that is called from the X +server's main dispatch loop when new events are available in the input +event queue. It typically processes the enqueued events, and updates +the cursor/pointer position. It may also do other DDX-specific event +processing. + + +Enqueued events are processed by mieqProcessInputEvents() and passed +to the DIX layer for transmission to clients: + + + +mieqProcessInputEvents() + +This function processes each event in the +event queue, and passes it to the device's input processing function. +The DIX layer provides default functions to do this processing, and they +handle the task of getting the events passed back to the relevant +clients. + + +miPointerUpdate() + +This function resynchronized the cursor position +with the new pointer position. It also takes care of moving the cursor +between screens when needed in multi-head configurations. + + + + + + + +DisableDevice() + +DisableDevice is a DIX function that removes an input device from the +list of enabled devices. The result of this is that the device no +longer generates input events. The device's data structures are kept in +place, and disabling a device like this can be reversed by calling +EnableDevice(). DisableDevice() may be called from the DDX when it is +desirable to do so (e.g., the XFree86 server does this when VT +switching). Except for special cases, this is not normally called for +core input devices. + + +DisableDevice() calls the device's callback function with +DEVICE_OFF: + + + +(*dev->deviceProc)(dev, DEVICE_OFF) + +This typically closes the +relevant physical device, and when appropriate, unregisters the device's +file descriptor (or equivalent) as a valid input source. + + + + +DisableDevice() then removes the device handle from the X server's +global list of enabled devices. + + + + + +CloseDevice() + +CloseDevice is a DIX function that removes an input device from the +list of available devices. It disables input from the device and frees +all data structures associated with the device. This function is +usually called from CloseDownDevices(), which is called from main() at +the end of each server generation to close all input devices. + + +CloseDevice() calls the device's callback function with +DEVICE_CLOSE: + + + +(*dev->deviceProc)(dev, DEVICE_CLOSE) + +This typically closes the +relevant physical device, and when appropriate, unregisters the device's +file descriptor (or equivalent) as a valid input source. If any device +specific data structures were allocated when the device was initialized, +they are freed here. + + + + +CloseDevice() then frees the data structures that were allocated +for the device when it was registered/initialized. + + + + + +LegalModifier() + +LegalModifier() is a required DDX function that can be used to +restrict which keys may be modifier keys. This seems to be present for +historical reasons, so this function should simply return TRUE +unconditionally. + + + + + + +Output handling + +The following sections describe the main functions required to +initialize, use and close the output device(s) for each screen in the X +server. + + + +InitOutput() + +This DDX function is called near the start of each server generation +from the X server's main() function. InitOutput()'s main purpose is to +initialize each screen and fill in the global screenInfo structure for +each screen. It is passed three arguments: a pointer to the screenInfo +struct, which it is to initialize, and argc and argv from main(), which +can be used to determine additional configuration information. + + +The primary tasks for this function are outlined below: + + + + Parse configuration info: The first task of InitOutput() + is to parses any configuration information from the configuration + file. In addition to the XF86Config file, other configuration + information can be taken from the command line. The command line + options can be gathered either in InitOutput() or earlier in the + ddxProcessArgument() function, which is called by + ProcessCommandLine(). The configuration information determines the + characteristics of the screen(s). For example, in the XFree86 X + server, the XF86Config file specifies the monitor information, the + screen resolution, the graphics devices and slots in which they are + located, and, for Xinerama, the screens' layout. + + + + + Initialize screen info: The next task is to initialize + the screen-dependent internal data structures. For example, part of + what the XFree86 X server does is to allocate its screen and pixmap + private indices, probe for graphics devices, compare the probed + devices to the ones listed in the XF86Config file, and add the ones that + match to the internal xf86Screens[] structure. + + + + + Set pixmap formats: The next task is to initialize the + screenInfo's image byte order, bitmap bit order and bitmap scanline + unit/pad. The screenInfo's pixmap format's depth, bits per pixel + and scanline padding is also initialized at this stage. + + + + + Unify screen info: An optional task that might be done at + this stage is to compare all of the information from the various + screens and determines if they are compatible (i.e., if the set of + screens can be unified into a single desktop). This task has + potential to be useful to the DMX front-end server, if Xinerama's + PanoramiXConsolidate() function is not sufficient. + + + + + +Once these tasks are complete, the valid screens are known and each +of these screens can be initialized by calling AddScreen(). + + + + +AddScreen() + +This DIX function is called from InitOutput(), in the DDX layer, to +add each new screen to the screenInfo structure. The DDX screen +initialization function and command line arguments (i.e., argc and argv) +are passed to it as arguments. + + +This function first allocates a new Screen structure and any privates +that are required. It then initializes some of the fields in the Screen +struct and sets up the pixmap padding information. Finally, it calls +the DDX screen initialization function ScreenInit(), which is described +below. It returns the number of the screen that were just added, or -1 +if there is insufficient memory to add the screen or if the DDX screen +initialization fails. + + + + +ScreenInit() + +This DDX function initializes the rest of the Screen structure with +either generic or screen-specific functions (as necessary). It also +fills in various screen attributes (e.g., width and height in +millimeters, black and white pixel values). + + +The screen init function usually calls several functions to perform +certain screen initialization functions. They are described below: + + + +{mi,*fb}ScreenInit() + +The DDX layer's ScreenInit() function usually +calls another layer's ScreenInit() function (e.g., miScreenInit() or +fbScreenInit()) to initialize the fallbacks that the DDX driver does not +specifically handle. + + +After calling another layer's ScreenInit() function, any +screen-specific functions either wrap or replace the other layer's +function pointers. If a function is to be wrapped, each of the old +function pointers from the other layer are stored in a screen private +area. Common functions to wrap are CloseScreen() and SaveScreen(). + + + +miInitializeBackingStore() + +This MI function initializes the +screen's backing storage functions, which are used to save areas of +windows that are currently covered by other windows. + + + +miDCInitialize() + +This MI function initializes the MI cursor +display structures and function pointers. If a hardware cursor is used, +the DDX layer's ScreenInit() function will wrap additional screen and +the MI cursor display function pointers. + + + + +Another common task for ScreenInit() function is to initialize the +output device state. For example, in the XFree86 X server, the +ScreenInit() function saves the original state of the video card and +then initializes the video mode of the graphics device. + + + + +CloseScreen() + +This function restores any wrapped screen functions (and in +particular the wrapped CloseScreen() function) and restores the state of +the output device to its original state. It should also free any +private data it created during the screen initialization. + + + + +GC operations + +When the X server is requested to render drawing primitives, it does +so by calling drawing functions through the graphics context's operation +function pointer table (i.e., the GCOps functions). These functions +render the basic graphics operations such as drawing rectangles, lines, +text or copying pixmaps. Default routines are provided either by the MI +layer, which draws indirectly through a simple span interface, or by the +framebuffer layers (e.g., CFB, MFB, FB), which draw directly to a +linearly mapped frame buffer. + + +To take advantage of special hardware on the graphics device, +specific GCOps functions can be replaced by device specific code. +However, many times the graphics devices can handle only a subset of the +possible states of the GC, so during graphics context validation, +appropriate routines are selected based on the state and capabilities of +the hardware. For example, some graphics hardware can accelerate single +pixel width lines with certain dash patterns. Thus, for dash patterns +that are not supported by hardware or for width 2 or greater lines, the +default routine is chosen during GC validation. + + +Note that some pointers to functions that draw to the screen are +stored in the Screen structure. They include GetImage(), GetSpans(), +CopyWindow() and RestoreAreas(). + + + + +Xnest + +The Xnest X server is a special proxy X server that relays the X +protocol requests that it receives to a ``real'' X server that then +processes the requests and displays the results, if applicable. To the X +applications, Xnest appears as if it is a regular X server. However, +Xnest is both server to the X application and client of the real X +server, which will actually handle the requests. + + +The Xnest server implements all of the standard input and output +initialization steps outlined above. + + + + +InitOutput() + +Xnest takes its configuration information from +command line arguments via ddxProcessArguments(). This information +includes the real X server display to connect to, its default visual +class, the screen depth, the Xnest window's geometry, etc. Xnest then +connects to the real X server and gathers visual, colormap, depth and +pixmap information about that server's display, creates a window on that +server, which will be used as the root window for Xnest. + + +Next, Xnest initializes its internal data structures and uses the +data from the real X server's pixmaps to initialize its own pixmap +formats. Finally, it calls AddScreen(xnestOpenScreen, argc, argv) to +initialize each of its screens. + + + +ScreenInit() + +Xnest's ScreenInit() function is called +xnestOpenScreen(). This function initializes its screen's depth and +visual information, and then calls miScreenInit() to set up the default +screen functions. It then calls miInitializeBackingStore() and +miDCInitialize() to initialize backing store and the software cursor. +Finally, it replaces many of the screen functions with its own +functions that repackage and send the requests to the real X server to +which Xnest is attached. + + + +CloseScreen() + +This function frees its internal data structure +allocations. Since it replaces instead of wrapping screen functions, +there are no function pointers to unwrap. This can potentially lead to +problems during server regeneration. + + + +GC operations + +The GC operations in Xnest are very simple since +they leave all of the drawing to the real X server to which Xnest is +attached. Each of the GCOps takes the request and sends it to the +real X server using standard Xlib calls. For example, the X +application issues a XDrawLines() call. This function turns into a +protocol request to Xnest, which calls the xnestPolylines() function +through Xnest's GCOps function pointer table. The xnestPolylines() +function is only a single line, which calls XDrawLines() using the same +arguments that were passed into it. Other GCOps functions are very +similar. Two exceptions to the simple GCOps functions described above +are the image functions and the BLT operations. + + +The image functions, GetImage() and PutImage(), must use a temporary +image to hold the image to be put of the image that was just grabbed +from the screen while it is in transit to the real X server or the +client. When the image has been transmitted, the temporary image is +destroyed. + + +The BLT operations, CopyArea() and CopyPlane(), handle not only the +copy function, which is the same as the simple cases described above, +but also the graphics exposures that result when the GC's graphics +exposure bit is set to True. Graphics exposures are handled in a helper +function, xnestBitBlitHelper(). This function collects the exposure +events from the real X server and, if any resulting in regions being +exposed, then those regions are passed back to the MI layer so that it +can generate exposure events for the X application. + + + + +The Xnest server takes its input from the X server to which it is +connected. When the mouse is in the Xnest server's window, keyboard and +mouse events are received by the Xnest server, repackaged and sent back +to any client that requests those events. + + + + +Shadow framebuffer + +The most common type of framebuffer is a linear array memory that +maps to the video memory on the graphics device. However, accessing +that video memory over an I/O bus (e.g., ISA or PCI) can be slow. The +shadow framebuffer layer allows the developer to keep the entire +framebuffer in main memory and copy it back to video memory at regular +intervals. It also has been extended to handle planar video memory and +rotated framebuffers. + + +There are two main entry points to the shadow framebuffer code: + + + +shadowAlloc(width, height, bpp) + +This function allocates the in +memory copy of the framebuffer of size width*height*bpp. It returns a +pointer to that memory, which will be used by the framebuffer +ScreenInit() code during the screen's initialization. + + + +shadowInit(pScreen, updateProc, windowProc) + +This function +initializes the shadow framebuffer layer. It wraps several screen +drawing functions, and registers a block handler that will update the +screen. The updateProc is a function that will copy the damaged regions +to the screen, and the windowProc is a function that is used when the +entire linear video memory range cannot be accessed simultaneously so +that only a window into that memory is available (e.g., when using the +VGA aperture). + + + + +The shadow framebuffer code keeps track of the damaged area of each +screen by calculating the bounding box of all drawing operations that +have occurred since the last screen update. Then, when the block handler +is next called, only the damaged portion of the screen is updated. + + +Note that since the shadow framebuffer is kept in main memory, all +drawing operations are performed by the CPU and, thus, no accelerated +hardware drawing operations are possible. + + + + + + +Xinerama + +Xinerama is an X extension that allows multiple physical screens +controlled by a single X server to appear as a single screen. Although +the extension allows clients to find the physical screen layout via +extension requests, it is completely transparent to clients at the core +X11 protocol level. The original public implementation of Xinerama came +from Digital/Compaq. XFree86 rewrote it, filling in some missing pieces +and improving both X11 core protocol compliance and performance. The +Xinerama extension will be passing through X.Org's standardization +process in the near future, and the sample implementation will be based +on this rewritten version. + + +The current implementation of Xinerama is based primarily in the DIX +(device independent) and MI (machine independent) layers of the X +server. With few exceptions the DDX layers do not need any changes to +support Xinerama. X server extensions often do need modifications to +provide full Xinerama functionality. + + +The following is a code-level description of how Xinerama functions. + + +Note: Because the Xinerama extension was originally called the +PanoramiX extension, many of the Xinerama functions still have the +PanoramiX prefix. + + + + +PanoramiXExtensionInit() + + PanoramiXExtensionInit() is a + device-independent extension function that is called at the start of + each server generation from InitExtensions(), which is called from + the X server's main() function after all output devices have been + initialized, but before any input devices have been initialized. + + + PanoramiXNumScreens is set to the number of physical screens. If + only one physical screen is present, the extension is disabled, and + PanoramiXExtensionInit() returns without doing anything else. + + + The Xinerama extension is registered by calling AddExtension(). + + + A local per-screen array of data structures + (panoramiXdataPtr[]) + is allocated for each physical screen, and GC and Screen private + indexes are allocated, and both GC and Screen private areas are + allocated for each physical screen. These hold Xinerama-specific + per-GC and per-Screen data. Each screen's CreateGC and CloseScreen + functions are wrapped by XineramaCreateGC() and + XineramaCloseScreen() respectively. Some new resource classes are + created for Xinerama drawables and GCs, and resource types for + Xinerama windows, pixmaps and colormaps. + + + A region (XineramaScreenRegions[i]) is initialized for each + physical screen, and single region (PanoramiXScreenRegion) is + initialized to be the union of the screen regions. The + panoramiXdataPtr[] array is also initialized with the size and + origin of each screen. The relative positioning information for the + physical screens is taken from the array + dixScreenOrigins[], which + the DDX layer must initialize in InitOutput(). The bounds of the + combined screen is also calculated (PanoramiXPixWidth and + PanoramiXPixHeight). + + + The DIX layer has a list of function pointers + (ProcVector[]) that + holds the entry points for the functions that process core protocol + requests. The requests that Xinerama must intercept and break up + into physical screen-specific requests are wrapped. The original + set is copied to SavedProcVector[]. The types of requests + intercepted are Window requests, GC requests, colormap requests, + drawing requests, and some geometry-related requests. This wrapping + allows the bulk of the protocol request processing to be handled + transparently to the DIX layer. Some operations cannot be dealt with + in this way and are handled with Xinerama-specific code within the + DIX layer. + + + + +PanoramiXConsolidate() + + PanoramiXConsolidate() is a + device-independent extension function that is called directly from + the X server's main() function after extensions and input/output + devices have been initialized, and before the root windows are + defined and initialized. + + + This function finds the set of depths (PanoramiXDepths[]) and + visuals (PanoramiXVisuals[]) + common to all of the physical screens. + PanoramiXNumDepths is set to the number of common depths, and + PanoramiXNumVisuals is set to the number of common visuals. + Resources are created for the single root window and the default + colormap. Each of these resources has per-physical screen entries. + + + + +PanoramiXCreateConnectionBlock() + + PanoramiXConsolidate() is a + device-independent extension function that is called directly from + the X server's main() function after the per-physical screen root + windows are created. It is called instead of the standard DIX + CreateConnectionBlock() function. If this function returns FALSE, + the X server exits with a fatal error. This function will return + FALSE if no common depths were found in PanoramiXConsolidate(). + With no common depths, Xinerama mode is not possible. + + + The connection block holds the information that clients get when + they open a connection to the X server. It includes information + such as the supported pixmap formats, number of screens and the + sizes, depths, visuals, default colormap information, etc, for each + of the screens (much of information that xdpyinfo shows). The + connection block is initialized with the combined single screen + values that were calculated in the above two functions. + + + The Xinerama extension allows the registration of connection + block callback functions. The purpose of these is to allow other + extensions to do processing at this point. These callbacks can be + registered by calling XineramaRegisterConnectionBlockCallback() from + the other extension's ExtensionInit() function. Each registered + connection block callback is called at the end of + PanoramiXCreateConnectionBlock(). + + + + + +Xinerama-specific changes to the DIX code + +There are a few types of Xinerama-specific changes within the DIX +code. The main ones are described here. + + +Functions that deal with colormap or GC -related operations outside of +the intercepted protocol requests have a test added to only do the +processing for screen numbers > 0. This is because they are handled for +the single Xinerama screen and the processing is done once for screen 0. + + +The handling of motion events does some coordinate translation between +the physical screen's origin and screen zero's origin. Also, motion +events must be reported relative to the composite screen origin rather +than the physical screen origins. + + +There is some special handling for cursor, window and event processing +that cannot (either not at all or not conveniently) be done via the +intercepted protocol requests. A particular case is the handling of +pointers moving between physical screens. + + + + +Xinerama-specific changes to the MI code + +The only Xinerama-specific change to the MI code is in miSendExposures() +to handle the coordinate (and window ID) translation for expose events. + + + + +Intercepted DIX core requests + +Xinerama breaks up drawing requests for dispatch to each physical +screen. It also breaks up windows into pieces for each physical screen. +GCs are translated into per-screen GCs. Colormaps are replicated on +each physical screen. The functions handling the intercepted requests +take care of breaking the requests and repackaging them so that they can +be passed to the standard request handling functions for each screen in +turn. In addition, and to aid the repackaging, the information from +many of the intercepted requests is used to keep up to date the +necessary state information for the single composite screen. Requests +(usually those with replies) that can be satisfied completely from this +stored state information do not call the standard request handling +functions. + + + + + + + + + + + +Development Results + +In this section the results of each phase of development are +discussed. This development took place between approximately June 2001 +and July 2003. + + + +Phase I + +The initial development phase dealt with the basic implementation +including the bootstrap code, which used the shadow framebuffer, and the +unoptimized implementation, based on an Xnest-style implementation. + + + +Scope + +The goal of Phase I is to provide fundamental functionality that can +act as a foundation for ongoing work: + + + Develop the proxy X server + + + The proxy X server will operate on the X11 protocol and + relay requests as necessary to correctly perform the request. + + + Work will be based on the existing work for Xinerama and + Xnest. + + + Input events and windowing operations are handled in the + proxy server and rendering requests are repackaged and sent to + each of the back-end servers for display. + + + The multiple screen layout (including support for + overlapping screens) will be user configurable via a + configuration file or through the configuration tool. + + + + + Develop graphical configuration tool + + + There will be potentially a large number of X servers to + configure into a single display. The tool will allow the user + to specify which servers are involved in the configuration and + how they should be laid out. + + + + + Pass the X Test Suite + + + The X Test Suite covers the basic X11 operations. All + tests known to succeed must correctly operate in the distributed + X environment. + + + + + + + +For this phase, the back-end X servers are assumed to be unmodified X +servers that do not support any DMX-related protocol extensions; future +optimization pathways are considered, but are not implemented; and the +configuration tool is assumed to rely only on libraries in the X source +tree (e.g., Xt). + + + + +Results + +The proxy X server, Xdmx, was developed to distribute X11 protocol +requests to the set of back-end X servers. It opens a window on each +back-end server, which represents the part of the front-end's root +window that is visible on that screen. It mirrors window, pixmap and +other state in each back-end server. Drawing requests are sent to +either windows or pixmaps on each back-end server. This code is based +on Xnest and uses the existing Xinerama extension. + + +Input events can be taken from (1) devices attached to the back-end +server, (2) core devices attached directly to the Xdmx server, or (3) +from a ``console'' window on another X server. Events for these devices +are gathered, processed and delivered to clients attached to the Xdmx +server. + + +An intuitive configuration format was developed to help the user +easily configure the multiple back-end X servers. It was defined (see +grammar in Xdmx man page) and a parser was implemented that is used by +the Xdmx server and by a standalone xdmxconfig utility. The parsing +support was implemented such that it can be easily factored out of the X +source tree for use with other tools (e.g., vdl). Support for +converting legacy vdl-format configuration files to the DMX format is +provided by the vdltodmx utility. + + +Originally, the configuration file was going to be a subsection of +XFree86's XF86Config file, but that was not possible since Xdmx is a +completely separate X server. Thus, a separate config file format was +developed. In addition, a graphical configuration +tool, xdmxconfig, was developed to allow the user to create and arrange +the screens in the configuration file. The -configfile and -config +command-line options can be used to start Xdmx using a configuration +file. + + +An extension that enables remote input testing is required for the X +Test Suite to function. During this phase, this extension (XTEST) was +implemented in the Xdmx server. The results from running the X Test +Suite are described in detail below. + + + + +X Test Suite + + + Introduction + + The X Test Suite contains tests that verify Xlib functions + operate correctly. The test suite is designed to run on a + single X server; however, since X applications will not be + able to tell the difference between the DMX server and a + standard X server, the X Test Suite should also run on the + DMX server. + + + The Xdmx server was tested with the X Test Suite, and the + existing failures are noted in this section. To put these + results in perspective, we first discuss expected X Test + failures and how errors in underlying systems can impact + Xdmx test results. + + + + + Expected Failures for a Single Head + + A correctly implemented X server with a single screen is + expected to fail certain X Test tests. The following + well-known errors occur because of rounding error in the X + server code: + +XDrawArc: Tests 42, 63, 66, 73 +XDrawArcs: Tests 45, 66, 69, 76 + + + + The following failures occur because of the high-level X + server implementation: + +XLoadQueryFont: Test 1 +XListFontsWithInfo: Tests 3, 4 +XQueryFont: Tests 1, 2 + + + + The following test fails when running the X server as root + under Linux because of the way directory modes are + interpreted: + +XWriteBitmapFile: Test 3 + + + + Depending on the video card used for the back-end, other + failures may also occur because of bugs in the low-level + driver implementation. Over time, failures of this kind + are usually fixed by XFree86, but will show up in Xdmx + testing until then. + + + + + Expected Failures for Xinerama + + Xinerama fails several X Test Suite tests because of + design decisions made for the current implementation of + Xinerama. Over time, many of these errors will be + corrected by XFree86 and the group working on a new + Xinerama implementation. Therefore, Xdmx will also share + X Suite Test failures with Xinerama. + + + + We may be able to fix or work-around some of these + failures at the Xdmx level, but this will require + additional exploration that was not part of Phase I. + + + + Xinerama is constantly improving, and the list of + Xinerama-related failures depends on XFree86 version and + the underlying graphics hardware. We tested with a + variety of hardware, including nVidia, S3, ATI Radeon, + and Matrox G400 (in dual-head mode). The list below + includes only those failures that appear to be from the + Xinerama layer, and does not include failures listed in + the previous section, or failures that appear to be from + the low-level graphics driver itself: + + + + These failures were noted with multiple Xinerama + configurations: + +XCopyPlane: Tests 13, 22, 31 (well-known Xinerama implementation issue) +XSetFontPath: Test 4 +XGetDefault: Test 5 +XMatchVisualInfo: Test 1 + + + + These failures were noted only when using one dual-head + video card with a 4.2.99.x XFree86 server: + +XListPixmapFormats: Test 1 +XDrawRectangles: Test 45 + + + + These failures were noted only when using two video cards + from different vendors with a 4.1.99.x XFree86 server: + +XChangeWindowAttributes: Test 32 +XCreateWindow: Test 30 +XDrawLine: Test 22 +XFillArc: Test 22 +XChangeKeyboardControl: Tests 9, 10 +XRebindKeysym: Test 1 + + + + + + Additional Failures from Xdmx + + + When running Xdmx, no unexpected failures were noted. + Since the Xdmx server is based on Xinerama, we expect to + have most of the Xinerama failures present in the Xdmx + server. Similarly, since the Xdmx server must rely on the + low-level device drivers on each back-end server, we also + expect that Xdmx will exhibit most of the back-end + failures. Here is a summary: + +XListPixmapFormats: Test 1 (configuration dependent) +XChangeWindowAttributes: Test 32 +XCreateWindow: Test 30 +XCopyPlane: Test 13, 22, 31 +XSetFontPath: Test 4 +XGetDefault: Test 5 (configuration dependent) +XMatchVisualInfo: Test 1 +XRebindKeysym: Test 1 (configuration dependent) + + + + Note that this list is shorter than the combined list for + Xinerama because Xdmx uses different code paths to perform + some Xinerama operations. Further, some Xinerama failures + have been fixed in the XFree86 4.2.99.x CVS repository. + + + + + Summary and Future Work + + + Running the X Test Suite on Xdmx does not produce any + failures that cannot be accounted for by the underlying + Xinerama subsystem used by the front-end or by the + low-level device-driver code running on the back-end X + servers. The Xdmx server therefore is as ``correct'' as + possible with respect to the standard set of X Test Suite + tests. + + + + During the following phases, we will continue to verify + Xdmx correctness using the X Test Suite. We may also use + other tests suites or write additional tests that run + under the X Test Suite that specifically verify the + expected behavior of DMX. + + + + + +Fonts + +In Phase I, fonts are handled directly by both the front-end and the +back-end servers, which is required since we must treat each back-end +server during this phase as a ``black box''. What this requires is that +the front- and back-end servers must share the exact same font +path. There are two ways to help make sure that all servers share the +same font path: + + + + First, each server can be configured to use the same font + server. The font server, xfs, can be configured to serve fonts to + multiple X servers via TCP. + + + + Second, each server can be configured to use the same font + path and either those font paths can be copied to each back-end + machine or they can be mounted (e.g., via NFS) on each back-end + machine. + + + + +One additional concern is that a client program can set its own font +path, and if it does so, then that font path must be available on each +back-end machine. + + +The -fontpath command line option was added to allow users to +initialize the font path of the front end server. This font path is +propagated to each back-end server when the default font is loaded. If +there are any problems, an error message is printed, which will describe +the problem and list the current font path. For more information about +setting the font path, see the -fontpath option description in the man +page. + + + + +Performance + +Phase I of development was not intended to optimize performance. Its +focus was on completely and correctly handling the base X11 protocol in +the Xdmx server. However, several insights were gained during Phase I, +which are listed here for reference during the next phase of +development. + + + + + Calls to XSync() can slow down rendering since it requires a + complete round trip to and from a back-end server. This is + especially problematic when communicating over long haul networks. + + + + Sending drawing requests to only the screens that they overlap + should improve performance. + + + + + +Pixmaps + +Pixmaps were originally expected to be handled entirely in the +front-end X server; however, it was found that this overly complicated +the rendering code and would have required sending potentially large +images to each back server that required them when copying from pixmap +to screen. Thus, pixmap state is mirrored in the back-end server just +as it is with regular window state. With this implementation, the same +rendering code that draws to windows can be used to draw to pixmaps on +the back-end server, and no large image transfers are required to copy +from pixmap to window. + + + + + + + + +Phase II + +The second phase of development concentrates on performance +optimizations. These optimizations are documented here, with +x11perf data to show how the optimizations improve performance. + + +All benchmarks were performed by running Xdmx on a dual processor +1.4GHz AMD Athlon machine with 1GB of RAM connecting over 100baseT to +two single-processor 1GHz Pentium III machines with 256MB of RAM and ATI +Rage 128 (RF) video cards. The front end was running Linux +2.4.20-pre1-ac1 and the back ends were running Linux 2.4.7-10 and +version 4.2.99.1 of XFree86 pulled from the XFree86 CVS repository on +August 7, 2002. All systems were running Red Hat Linux 7.2. + + + +Moving from XFree86 4.1.99.1 to 4.2.0.0 + +For phase II, the working source tree was moved to the branch tagged +with dmx-1-0-branch and was updated from version 4.1.99.1 (20 August +2001) of the XFree86 sources to version 4.2.0.0 (18 January 2002). +After this update, the following tests were noted to be more than 10% +faster: + +1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple) +1.16 Fill 1x1 tiled trapezoid (161x145 tile) +1.13 Fill 10x10 tiled trapezoid (161x145 tile) +1.17 Fill 100x100 tiled trapezoid (161x145 tile) +1.16 Fill 1x1 tiled trapezoid (216x208 tile) +1.20 Fill 10x10 tiled trapezoid (216x208 tile) +1.15 Fill 100x100 tiled trapezoid (216x208 tile) +1.37 Circulate Unmapped window (200 kids) + +And the following tests were noted to be more than 10% slower: + +0.88 Unmap window via parent (25 kids) +0.75 Circulate Unmapped window (4 kids) +0.79 Circulate Unmapped window (16 kids) +0.80 Circulate Unmapped window (25 kids) +0.82 Circulate Unmapped window (50 kids) +0.85 Circulate Unmapped window (75 kids) + + + +These changes were not caused by any changes in the DMX system, and +may point to changes in the XFree86 tree or to tests that have more +"jitter" than most other x11perf tests. + + + + +Global changes + +During the development of the Phase II DMX server, several global +changes were made. These changes were also compared with the Phase I +server. The following tests were noted to be more than 10% faster: + +1.13 Fill 300x300 opaque stippled trapezoid (161x145 stipple) +1.15 Fill 1x1 tiled trapezoid (161x145 tile) +1.13 Fill 10x10 tiled trapezoid (161x145 tile) +1.17 Fill 100x100 tiled trapezoid (161x145 tile) +1.16 Fill 1x1 tiled trapezoid (216x208 tile) +1.19 Fill 10x10 tiled trapezoid (216x208 tile) +1.15 Fill 100x100 tiled trapezoid (216x208 tile) +1.15 Circulate Unmapped window (4 kids) + + + +The following tests were noted to be more than 10% slower: + +0.69 Scroll 10x10 pixels +0.68 Scroll 100x100 pixels +0.68 Copy 10x10 from window to window +0.68 Copy 100x100 from window to window +0.76 Circulate Unmapped window (75 kids) +0.83 Circulate Unmapped window (100 kids) + + + +For the remainder of this analysis, the baseline of comparison will +be the Phase II deliverable with all optimizations disabled (unless +otherwise noted). This will highlight how the optimizations in +isolation impact performance. + + + + +XSync() Batching + +During the Phase I implementation, XSync() was called after every +protocol request made by the DMX server. This provided the DMX server +with an interactive feel, but defeated X11's protocol buffering system +and introduced round-trip wire latency into every operation. During +Phase II, DMX was changed so that protocol requests are no longer +followed by calls to XSync(). Instead, the need for an XSync() is +noted, and XSync() calls are only made every 100mS or when the DMX +server specifically needs to make a call to guarantee interactivity. +With this new system, X11 buffers protocol as much as possible during a +100mS interval, and many unnecessary XSync() calls are avoided. + + +Out of more than 300 x11perf tests, 8 tests became more than 100 +times faster, with 68 more than 50X faster, 114 more than 10X faster, +and 181 more than 2X faster. See table below for summary. + + +The following tests were noted to be more than 10% slower with +XSync() batching on: + +0.88 500x500 tiled rectangle (161x145 tile) +0.89 Copy 500x500 from window to window + + + + + +Offscreen Optimization + +Windows span one or more of the back-end servers' screens; however, +during Phase I development, windows were created on every back-end +server and every rendering request was sent to every window regardless +of whether or not that window was visible. With the offscreen +optimization, the DMX server tracks when a window is completely off of a +back-end server's screen and, in that case, it does not send rendering +requests to those back-end windows. This optimization saves bandwidth +between the front and back-end servers, and it reduces the number of +XSync() calls. The performance tests were run on a DMX system with only +two back-end servers. Greater performance gains will be had as the +number of back-end servers increases. + + +Out of more than 300 x11perf tests, 3 tests were at least twice as +fast, and 146 tests were at least 10% faster. Two tests were more than +10% slower with the offscreen optimization: + +0.88 Hide/expose window via popup (4 kids) +0.89 Resize unmapped window (75 kids) + + + + + +Lazy Window Creation Optimization + +As mentioned above, during Phase I, windows were created on every +back-end server even if they were not visible on that back-end. With +the lazy window creation optimization, the DMX server does not create +windows on a back-end server until they are either visible or they +become the parents of a visible window. This optimization builds on the +offscreen optimization (described above) and requires it to be enabled. + + +The lazy window creation optimization works by creating the window +data structures in the front-end server when a client creates a window, +but delays creation of the window on the back-end server(s). A private +window structure in the DMX server saves the relevant window data and +tracks changes to the window's attributes and stacking order for later +use. The only times a window is created on a back-end server are (1) +when it is mapped and is at least partially overlapping the back-end +server's screen (tracked by the offscreen optimization), or (2) when the +window becomes the parent of a previously visible window. The first +case occurs when a window is mapped or when a visible window is copied, +moved or resized and now overlaps the back-end server's screen. The +second case occurs when starting a window manager after having created +windows to which the window manager needs to add decorations. + + +When either case occurs, a window on the back-end server is created +using the data saved in the DMX server's window private data structure. +The stacking order is then adjusted to correctly place the window on the +back-end and lastly the window is mapped. From this time forward, the +window is handled exactly as if the window had been created at the time +of the client's request. + + +Note that when a window is no longer visible on a back-end server's +screen (e.g., it is moved offscreen), the window is not destroyed; +rather, it is kept and reused later if the window once again becomes +visible on the back-end server's screen. Originally with this +optimization, destroying windows was implemented but was later rejected +because it increased bandwidth when windows were opaquely moved or +resized, which is common in many window managers. + + +The performance tests were run on a DMX system with only two back-end +servers. Greater performance gains will be had as the number of +back-end servers increases. + + +This optimization improved the following x11perf tests by more +than 10%: + +1.10 500x500 rectangle outline +1.12 Fill 100x100 stippled trapezoid (161x145 stipple) +1.20 Circulate Unmapped window (50 kids) +1.19 Circulate Unmapped window (75 kids) + + + + + +Subdividing Rendering Primitives + +X11 imaging requests transfer significant data between the client and +the X server. During Phase I, the DMX server would then transfer the +image data to each back-end server. Even with the offscreen +optimization (above), these requests still required transferring +significant data to each back-end server that contained a visible +portion of the window. For example, if the client uses XPutImage() to +copy an image to a window that overlaps the entire DMX screen, then the +entire image is copied by the DMX server to every back-end server. + + +To reduce the amount of data transferred between the DMX server and +the back-end servers when XPutImage() is called, the image data is +subdivided and only the data that will be visible on a back-end server's +screen is sent to that back-end server. Xinerama already implements a +subdivision algorithm for XGetImage() and no further optimization was +needed. + + +Other rendering primitives were analyzed, but the time required to +subdivide these primitives was a significant proportion of the time +required to send the entire rendering request to the back-end server, so +this optimization was rejected for the other rendering primitives. + + +Again, the performance tests were run on a DMX system with only two +back-end servers. Greater performance gains will be had as the number +of back-end servers increases. + + +This optimization improved the following x11perf tests by more +than 10%: + +1.12 Fill 100x100 stippled trapezoid (161x145 stipple) +1.26 PutImage 10x10 square +1.83 PutImage 100x100 square +1.91 PutImage 500x500 square +1.40 PutImage XY 10x10 square +1.48 PutImage XY 100x100 square +1.50 PutImage XY 500x500 square +1.45 Circulate Unmapped window (75 kids) +1.74 Circulate Unmapped window (100 kids) + + + +The following test was noted to be more than 10% slower with this +optimization: + +0.88 10-pixel fill chord partial circle + + + + + +Summary of x11perf Data + +With all of the optimizations on, 53 x11perf tests are more than +100X faster than the unoptimized Phase II deliverable, with 69 more than +50X faster, 73 more than 10X faster, and 199 more than twice as fast. +No tests were more than 10% slower than the unoptimized Phase II +deliverable. (Compared with the Phase I deliverable, only Circulate +Unmapped window (100 kids) was more than 10% slower than the Phase II +deliverable. As noted above, this test seems to have wider variability +than other x11perf tests.) + + +The following table summarizes relative x11perf test changes for +all optimizations individually and collectively. Note that some of the +optimizations have a synergistic effect when used together. + + +1: XSync() batching only +2: Off screen optimizations only +3: Window optimizations only +4: Subdivprims only +5: All optimizations + + 1 2 3 4 5 Operation +------ ---- ---- ---- ------ --------- + 2.14 1.85 1.00 1.00 4.13 Dot + 1.67 1.80 1.00 1.00 3.31 1x1 rectangle + 2.38 1.43 1.00 1.00 2.44 10x10 rectangle + 1.00 1.00 0.92 0.98 1.00 100x100 rectangle + 1.00 1.00 1.00 1.00 1.00 500x500 rectangle + 1.83 1.85 1.05 1.06 3.54 1x1 stippled rectangle (8x8 stipple) + 2.43 1.43 1.00 1.00 2.41 10x10 stippled rectangle (8x8 stipple) + 0.98 1.00 1.00 1.00 1.00 100x100 stippled rectangle (8x8 stipple) + 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (8x8 stipple) + 1.75 1.75 1.00 1.00 3.40 1x1 opaque stippled rectangle (8x8 stipple) + 2.38 1.42 1.00 1.00 2.34 10x10 opaque stippled rectangle (8x8 stipple) + 1.00 1.00 0.97 0.97 1.00 100x100 opaque stippled rectangle (8x8 stipple) + 1.00 1.00 1.00 1.00 0.99 500x500 opaque stippled rectangle (8x8 stipple) + 1.82 1.82 1.04 1.04 3.56 1x1 tiled rectangle (4x4 tile) + 2.33 1.42 1.00 1.00 2.37 10x10 tiled rectangle (4x4 tile) + 1.00 0.92 1.00 1.00 1.00 100x100 tiled rectangle (4x4 tile) + 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (4x4 tile) + 1.94 1.62 1.00 1.00 3.66 1x1 stippled rectangle (17x15 stipple) + 1.74 1.28 1.00 1.00 1.73 10x10 stippled rectangle (17x15 stipple) + 1.00 1.00 1.00 0.89 0.98 100x100 stippled rectangle (17x15 stipple) + 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (17x15 stipple) + 1.94 1.62 1.00 1.00 3.67 1x1 opaque stippled rectangle (17x15 stipple) + 1.69 1.26 1.00 1.00 1.66 10x10 opaque stippled rectangle (17x15 stipple) + 1.00 0.95 1.00 1.00 1.00 100x100 opaque stippled rectangle (17x15 stipple) + 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (17x15 stipple) + 1.93 1.61 0.99 0.99 3.69 1x1 tiled rectangle (17x15 tile) + 1.73 1.27 1.00 1.00 1.72 10x10 tiled rectangle (17x15 tile) + 1.00 1.00 1.00 1.00 0.98 100x100 tiled rectangle (17x15 tile) + 1.00 1.00 0.97 0.97 1.00 500x500 tiled rectangle (17x15 tile) + 1.95 1.63 1.00 1.00 3.83 1x1 stippled rectangle (161x145 stipple) + 1.80 1.30 1.00 1.00 1.83 10x10 stippled rectangle (161x145 stipple) + 0.97 1.00 1.00 1.00 1.01 100x100 stippled rectangle (161x145 stipple) + 1.00 1.00 1.00 1.00 0.98 500x500 stippled rectangle (161x145 stipple) + 1.95 1.63 1.00 1.00 3.56 1x1 opaque stippled rectangle (161x145 stipple) + 1.65 1.25 1.00 1.00 1.68 10x10 opaque stippled rectangle (161x145 stipple) + 1.00 1.00 1.00 1.00 1.01 100x100 opaque stippled rectangle (161x145... + 1.00 1.00 1.00 1.00 0.97 500x500 opaque stippled rectangle (161x145... + 1.95 1.63 0.98 0.99 3.80 1x1 tiled rectangle (161x145 tile) + 1.67 1.26 1.00 1.00 1.67 10x10 tiled rectangle (161x145 tile) + 1.13 1.14 1.14 1.14 1.14 100x100 tiled rectangle (161x145 tile) + 0.88 1.00 1.00 1.00 0.99 500x500 tiled rectangle (161x145 tile) + 1.93 1.63 1.00 1.00 3.53 1x1 tiled rectangle (216x208 tile) + 1.69 1.26 1.00 1.00 1.66 10x10 tiled rectangle (216x208 tile) + 1.00 1.00 1.00 1.00 1.00 100x100 tiled rectangle (216x208 tile) + 1.00 1.00 1.00 1.00 1.00 500x500 tiled rectangle (216x208 tile) + 1.82 1.70 1.00 1.00 3.38 1-pixel line segment + 2.07 1.56 0.90 1.00 3.31 10-pixel line segment + 1.29 1.10 1.00 1.00 1.27 100-pixel line segment + 1.05 1.06 1.03 1.03 1.09 500-pixel line segment + 1.30 1.13 1.00 1.00 1.29 100-pixel line segment (1 kid) + 1.32 1.15 1.00 1.00 1.32 100-pixel line segment (2 kids) + 1.33 1.16 1.00 1.00 1.33 100-pixel line segment (3 kids) + 1.92 1.64 1.00 1.00 3.73 10-pixel dashed segment + 1.34 1.16 1.00 1.00 1.34 100-pixel dashed segment + 1.24 1.11 0.99 0.97 1.23 100-pixel double-dashed segment + 1.72 1.77 1.00 1.00 3.25 10-pixel horizontal line segment + 1.83 1.66 1.01 1.00 3.54 100-pixel horizontal line segment + 1.86 1.30 1.00 1.00 1.84 500-pixel horizontal line segment + 2.11 1.52 1.00 0.99 3.02 10-pixel vertical line segment + 1.21 1.10 1.00 1.00 1.20 100-pixel vertical line segment + 1.03 1.03 1.00 1.00 1.02 500-pixel vertical line segment + 4.42 1.68 1.00 1.01 4.64 10x1 wide horizontal line segment + 1.83 1.31 1.00 1.00 1.83 100x10 wide horizontal line segment + 1.07 1.00 0.96 1.00 1.07 500x50 wide horizontal line segment + 4.10 1.67 1.00 1.00 4.62 10x1 wide vertical line segment + 1.50 1.24 1.06 1.06 1.48 100x10 wide vertical line segment + 1.06 1.03 1.00 1.00 1.05 500x50 wide vertical line segment + 2.54 1.61 1.00 1.00 3.61 1-pixel line + 2.71 1.48 1.00 1.00 2.67 10-pixel line + 1.19 1.09 1.00 1.00 1.19 100-pixel line + 1.04 1.02 1.00 1.00 1.03 500-pixel line + 2.68 1.51 0.98 1.00 3.17 10-pixel dashed line + 1.23 1.11 0.99 0.99 1.23 100-pixel dashed line + 1.15 1.08 1.00 1.00 1.15 100-pixel double-dashed line + 2.27 1.39 1.00 1.00 2.23 10x1 wide line + 1.20 1.09 1.00 1.00 1.20 100x10 wide line + 1.04 1.02 1.00 1.00 1.04 500x50 wide line + 1.52 1.45 1.00 1.00 1.52 100x10 wide dashed line + 1.54 1.47 1.00 1.00 1.54 100x10 wide double-dashed line + 1.97 1.30 0.96 0.95 1.95 10x10 rectangle outline + 1.44 1.27 1.00 1.00 1.43 100x100 rectangle outline + 3.22 2.16 1.10 1.09 3.61 500x500 rectangle outline + 1.95 1.34 1.00 1.00 1.90 10x10 wide rectangle outline + 1.14 1.14 1.00 1.00 1.13 100x100 wide rectangle outline + 1.00 1.00 1.00 1.00 1.00 500x500 wide rectangle outline + 1.57 1.72 1.00 1.00 3.03 1-pixel circle + 1.96 1.35 1.00 1.00 1.92 10-pixel circle + 1.21 1.07 0.86 0.97 1.20 100-pixel circle + 1.08 1.04 1.00 1.00 1.08 500-pixel circle + 1.39 1.19 1.03 1.03 1.38 100-pixel dashed circle + 1.21 1.11 1.00 1.00 1.23 100-pixel double-dashed circle + 1.59 1.28 1.00 1.00 1.58 10-pixel wide circle + 1.22 1.12 0.99 1.00 1.22 100-pixel wide circle + 1.06 1.04 1.00 1.00 1.05 500-pixel wide circle + 1.87 1.84 1.00 1.00 1.85 100-pixel wide dashed circle + 1.90 1.93 1.01 1.01 1.90 100-pixel wide double-dashed circle + 2.13 1.43 1.00 1.00 2.32 10-pixel partial circle + 1.42 1.18 1.00 1.00 1.42 100-pixel partial circle + 1.92 1.85 1.01 1.01 1.89 10-pixel wide partial circle + 1.73 1.67 1.00 1.00 1.73 100-pixel wide partial circle + 1.36 1.95 1.00 1.00 2.64 1-pixel solid circle + 2.02 1.37 1.00 1.00 2.03 10-pixel solid circle + 1.19 1.09 1.00 1.00 1.19 100-pixel solid circle + 1.02 0.99 1.00 1.00 1.01 500-pixel solid circle + 1.74 1.28 1.00 0.88 1.73 10-pixel fill chord partial circle + 1.31 1.13 1.00 1.00 1.31 100-pixel fill chord partial circle + 1.67 1.31 1.03 1.03 1.72 10-pixel fill slice partial circle + 1.30 1.13 1.00 1.00 1.28 100-pixel fill slice partial circle + 2.45 1.49 1.01 1.00 2.71 10-pixel ellipse + 1.22 1.10 1.00 1.00 1.22 100-pixel ellipse + 1.09 1.04 1.00 1.00 1.09 500-pixel ellipse + 1.90 1.28 1.00 1.00 1.89 100-pixel dashed ellipse + 1.62 1.24 0.96 0.97 1.61 100-pixel double-dashed ellipse + 2.43 1.50 1.00 1.00 2.42 10-pixel wide ellipse + 1.61 1.28 1.03 1.03 1.60 100-pixel wide ellipse + 1.08 1.05 1.00 1.00 1.08 500-pixel wide ellipse + 1.93 1.88 1.00 1.00 1.88 100-pixel wide dashed ellipse + 1.94 1.89 1.01 1.00 1.94 100-pixel wide double-dashed ellipse + 2.31 1.48 1.00 1.00 2.67 10-pixel partial ellipse + 1.38 1.17 1.00 1.00 1.38 100-pixel partial ellipse + 2.00 1.85 0.98 0.97 1.98 10-pixel wide partial ellipse + 1.89 1.86 1.00 1.00 1.89 100-pixel wide partial ellipse + 3.49 1.60 1.00 1.00 3.65 10-pixel filled ellipse + 1.67 1.26 1.00 1.00 1.67 100-pixel filled ellipse + 1.06 1.04 1.00 1.00 1.06 500-pixel filled ellipse + 2.38 1.43 1.01 1.00 2.32 10-pixel fill chord partial ellipse + 2.06 1.30 1.00 1.00 2.05 100-pixel fill chord partial ellipse + 2.27 1.41 1.00 1.00 2.27 10-pixel fill slice partial ellipse + 1.98 1.33 1.00 0.97 1.97 100-pixel fill slice partial ellipse + 57.46 1.99 1.01 1.00 114.92 Fill 1x1 equivalent triangle + 56.94 1.98 1.01 1.00 73.89 Fill 10x10 equivalent triangle + 6.07 1.75 1.00 1.00 6.07 Fill 100x100 equivalent triangle + 51.12 1.98 1.00 1.00 102.81 Fill 1x1 trapezoid + 51.42 1.82 1.01 1.00 94.89 Fill 10x10 trapezoid + 6.47 1.80 1.00 1.00 6.44 Fill 100x100 trapezoid + 1.56 1.28 1.00 0.99 1.56 Fill 300x300 trapezoid + 51.27 1.97 0.96 0.97 102.54 Fill 1x1 stippled trapezoid (8x8 stipple) + 51.73 2.00 1.02 1.02 67.92 Fill 10x10 stippled trapezoid (8x8 stipple) + 5.36 1.72 1.00 1.00 5.36 Fill 100x100 stippled trapezoid (8x8 stipple) + 1.54 1.26 1.00 1.00 1.59 Fill 300x300 stippled trapezoid (8x8 stipple) + 51.41 1.94 1.01 1.00 102.82 Fill 1x1 opaque stippled trapezoid (8x8 stipple) + 50.71 1.95 0.99 1.00 65.44 Fill 10x10 opaque stippled trapezoid (8x8... + 5.33 1.73 1.00 1.00 5.36 Fill 100x100 opaque stippled trapezoid (8x8... + 1.58 1.25 1.00 1.00 1.58 Fill 300x300 opaque stippled trapezoid (8x8... + 51.56 1.96 0.99 0.90 103.68 Fill 1x1 tiled trapezoid (4x4 tile) + 51.59 1.99 1.01 1.01 62.25 Fill 10x10 tiled trapezoid (4x4 tile) + 5.38 1.72 1.00 1.00 5.38 Fill 100x100 tiled trapezoid (4x4 tile) + 1.54 1.25 1.00 0.99 1.58 Fill 300x300 tiled trapezoid (4x4 tile) + 51.70 1.98 1.01 1.01 103.98 Fill 1x1 stippled trapezoid (17x15 stipple) + 44.86 1.97 1.00 1.00 44.86 Fill 10x10 stippled trapezoid (17x15 stipple) + 2.74 1.56 1.00 1.00 2.73 Fill 100x100 stippled trapezoid (17x15 stipple) + 1.29 1.14 1.00 1.00 1.27 Fill 300x300 stippled trapezoid (17x15 stipple) + 51.41 1.96 0.96 0.95 103.39 Fill 1x1 opaque stippled trapezoid (17x15... + 45.14 1.96 1.01 1.00 45.14 Fill 10x10 opaque stippled trapezoid (17x15... + 2.68 1.56 1.00 1.00 2.68 Fill 100x100 opaque stippled trapezoid (17x15... + 1.26 1.10 1.00 1.00 1.28 Fill 300x300 opaque stippled trapezoid (17x15... + 51.13 1.97 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (17x15 tile) + 47.58 1.96 1.00 1.00 47.86 Fill 10x10 tiled trapezoid (17x15 tile) + 2.74 1.56 1.00 1.00 2.74 Fill 100x100 tiled trapezoid (17x15 tile) + 1.29 1.14 1.00 1.00 1.28 Fill 300x300 tiled trapezoid (17x15 tile) + 51.13 1.97 0.99 0.97 103.39 Fill 1x1 stippled trapezoid (161x145 stipple) + 45.14 1.97 1.00 1.00 44.29 Fill 10x10 stippled trapezoid (161x145 stipple) + 3.02 1.77 1.12 1.12 3.38 Fill 100x100 stippled trapezoid (161x145 stipple) + 1.31 1.13 1.00 1.00 1.30 Fill 300x300 stippled trapezoid (161x145 stipple) + 51.27 1.97 1.00 1.00 103.10 Fill 1x1 opaque stippled trapezoid (161x145... + 45.01 1.97 1.00 1.00 45.01 Fill 10x10 opaque stippled trapezoid (161x145... + 2.67 1.56 1.00 1.00 2.69 Fill 100x100 opaque stippled trapezoid (161x145.. + 1.29 1.13 1.00 1.01 1.27 Fill 300x300 opaque stippled trapezoid (161x145.. + 51.41 1.96 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (161x145 tile) + 45.01 1.96 0.98 1.00 45.01 Fill 10x10 tiled trapezoid (161x145 tile) + 2.62 1.36 1.00 1.00 2.69 Fill 100x100 tiled trapezoid (161x145 tile) + 1.27 1.13 1.00 1.00 1.22 Fill 300x300 tiled trapezoid (161x145 tile) + 51.13 1.98 1.00 1.00 103.39 Fill 1x1 tiled trapezoid (216x208 tile) + 45.14 1.97 1.01 0.99 45.14 Fill 10x10 tiled trapezoid (216x208 tile) + 2.62 1.55 1.00 1.00 2.71 Fill 100x100 tiled trapezoid (216x208 tile) + 1.28 1.13 1.00 1.00 1.20 Fill 300x300 tiled trapezoid (216x208 tile) + 50.71 1.95 1.00 1.00 54.70 Fill 10x10 equivalent complex polygon + 5.51 1.71 0.96 0.98 5.47 Fill 100x100 equivalent complex polygons + 8.39 1.97 1.00 1.00 16.75 Fill 10x10 64-gon (Convex) + 8.38 1.83 1.00 1.00 8.43 Fill 100x100 64-gon (Convex) + 8.50 1.96 1.00 1.00 16.64 Fill 10x10 64-gon (Complex) + 8.26 1.83 1.00 1.00 8.35 Fill 100x100 64-gon (Complex) + 14.09 1.87 1.00 1.00 14.05 Char in 80-char line (6x13) + 11.91 1.87 1.00 1.00 11.95 Char in 70-char line (8x13) + 11.16 1.85 1.01 1.00 11.10 Char in 60-char line (9x15) + 10.09 1.78 1.00 1.00 10.09 Char16 in 40-char line (k14) + 6.15 1.75 1.00 1.00 6.31 Char16 in 23-char line (k24) + 11.92 1.90 1.03 1.03 11.88 Char in 80-char line (TR 10) + 8.18 1.78 1.00 0.99 8.17 Char in 30-char line (TR 24) + 42.83 1.44 1.01 1.00 42.11 Char in 20/40/20 line (6x13, TR 10) + 27.45 1.43 1.01 1.01 27.45 Char16 in 7/14/7 line (k14, k24) + 12.13 1.85 1.00 1.00 12.05 Char in 80-char image line (6x13) + 10.00 1.84 1.00 1.00 10.00 Char in 70-char image line (8x13) + 9.18 1.83 1.00 1.00 9.12 Char in 60-char image line (9x15) + 9.66 1.82 0.98 0.95 9.66 Char16 in 40-char image line (k14) + 5.82 1.72 1.00 1.00 5.99 Char16 in 23-char image line (k24) + 8.70 1.80 1.00 1.00 8.65 Char in 80-char image line (TR 10) + 4.67 1.66 1.00 1.00 4.67 Char in 30-char image line (TR 24) + 84.43 1.47 1.00 1.00 124.18 Scroll 10x10 pixels + 3.73 1.50 1.00 0.98 3.73 Scroll 100x100 pixels + 1.00 1.00 1.00 1.00 1.00 Scroll 500x500 pixels + 84.43 1.51 1.00 1.00 134.02 Copy 10x10 from window to window + 3.62 1.51 0.98 0.98 3.62 Copy 100x100 from window to window + 0.89 1.00 1.00 1.00 1.00 Copy 500x500 from window to window + 57.06 1.99 1.00 1.00 88.64 Copy 10x10 from pixmap to window + 2.49 2.00 1.00 1.00 2.48 Copy 100x100 from pixmap to window + 1.00 0.91 1.00 1.00 0.98 Copy 500x500 from pixmap to window + 2.04 1.01 1.00 1.00 2.03 Copy 10x10 from window to pixmap + 1.05 1.00 1.00 1.00 1.05 Copy 100x100 from window to pixmap + 1.00 1.00 0.93 1.00 1.04 Copy 500x500 from window to pixmap + 58.52 1.03 1.03 1.02 57.95 Copy 10x10 from pixmap to pixmap + 2.40 1.00 1.00 1.00 2.45 Copy 100x100 from pixmap to pixmap + 1.00 1.00 1.00 1.00 1.00 Copy 500x500 from pixmap to pixmap + 51.57 1.92 1.00 1.00 85.75 Copy 10x10 1-bit deep plane + 6.37 1.75 1.01 1.01 6.37 Copy 100x100 1-bit deep plane + 1.26 1.11 1.00 1.00 1.24 Copy 500x500 1-bit deep plane + 4.23 1.63 0.98 0.97 4.38 Copy 10x10 n-bit deep plane + 1.04 1.02 1.00 1.00 1.04 Copy 100x100 n-bit deep plane + 1.00 1.00 1.00 1.00 1.00 Copy 500x500 n-bit deep plane + 6.45 1.98 1.00 1.26 12.80 PutImage 10x10 square + 1.10 1.87 1.00 1.83 2.11 PutImage 100x100 square + 1.02 1.93 1.00 1.91 1.91 PutImage 500x500 square + 4.17 1.78 1.00 1.40 7.18 PutImage XY 10x10 square + 1.27 1.49 0.97 1.48 2.10 PutImage XY 100x100 square + 1.00 1.50 1.00 1.50 1.52 PutImage XY 500x500 square + 1.07 1.01 1.00 1.00 1.06 GetImage 10x10 square + 1.01 1.00 1.00 1.00 1.01 GetImage 100x100 square + 1.00 1.00 1.00 1.00 1.00 GetImage 500x500 square + 1.56 1.00 0.99 0.97 1.56 GetImage XY 10x10 square + 1.02 1.00 1.00 1.00 1.02 GetImage XY 100x100 square + 1.00 1.00 1.00 1.00 1.00 GetImage XY 500x500 square + 1.00 1.00 1.01 0.98 0.95 X protocol NoOperation + 1.02 1.03 1.04 1.03 1.00 QueryPointer + 1.03 1.02 1.04 1.03 1.00 GetProperty +100.41 1.51 1.00 1.00 198.76 Change graphics context + 45.81 1.00 0.99 0.97 57.10 Create and map subwindows (4 kids) + 78.45 1.01 1.02 1.02 63.07 Create and map subwindows (16 kids) + 73.91 1.01 1.00 1.00 56.37 Create and map subwindows (25 kids) + 73.22 1.00 1.00 1.00 49.07 Create and map subwindows (50 kids) + 72.36 1.01 0.99 1.00 32.14 Create and map subwindows (75 kids) + 70.34 1.00 1.00 1.00 30.12 Create and map subwindows (100 kids) + 55.00 1.00 1.00 0.99 23.75 Create and map subwindows (200 kids) + 55.30 1.01 1.00 1.00 141.03 Create unmapped window (4 kids) + 55.38 1.01 1.01 1.00 163.25 Create unmapped window (16 kids) + 54.75 0.96 1.00 0.99 166.95 Create unmapped window (25 kids) + 54.83 1.00 1.00 0.99 178.81 Create unmapped window (50 kids) + 55.38 1.01 1.01 1.00 181.20 Create unmapped window (75 kids) + 55.38 1.01 1.01 1.00 181.20 Create unmapped window (100 kids) + 54.87 1.01 1.01 1.00 182.05 Create unmapped window (200 kids) + 28.13 1.00 1.00 1.00 30.75 Map window via parent (4 kids) + 36.14 1.01 1.01 1.01 32.58 Map window via parent (16 kids) + 26.13 1.00 0.98 0.95 29.85 Map window via parent (25 kids) + 40.07 1.00 1.01 1.00 27.57 Map window via parent (50 kids) + 23.26 0.99 1.00 1.00 18.23 Map window via parent (75 kids) + 22.91 0.99 1.00 0.99 16.52 Map window via parent (100 kids) + 27.79 1.00 1.00 0.99 12.50 Map window via parent (200 kids) + 22.35 1.00 1.00 1.00 56.19 Unmap window via parent (4 kids) + 9.57 1.00 0.99 1.00 89.78 Unmap window via parent (16 kids) + 80.77 1.01 1.00 1.00 103.85 Unmap window via parent (25 kids) + 96.34 1.00 1.00 1.00 116.06 Unmap window via parent (50 kids) + 99.72 1.00 1.00 1.00 124.93 Unmap window via parent (75 kids) +112.36 1.00 1.00 1.00 125.27 Unmap window via parent (100 kids) +105.41 1.00 1.00 0.99 120.00 Unmap window via parent (200 kids) + 51.29 1.03 1.02 1.02 74.19 Destroy window via parent (4 kids) + 86.75 0.99 0.99 0.99 116.87 Destroy window via parent (16 kids) +106.43 1.01 1.01 1.01 127.49 Destroy window via parent (25 kids) +120.34 1.01 1.01 1.00 140.11 Destroy window via parent (50 kids) +126.67 1.00 0.99 0.99 145.00 Destroy window via parent (75 kids) +126.11 1.01 1.01 1.00 140.56 Destroy window via parent (100 kids) +128.57 1.01 1.00 1.00 137.91 Destroy window via parent (200 kids) + 16.04 0.88 1.00 1.00 20.36 Hide/expose window via popup (4 kids) + 19.04 1.01 1.00 1.00 23.48 Hide/expose window via popup (16 kids) + 19.22 1.00 1.00 1.00 20.44 Hide/expose window via popup (25 kids) + 17.41 1.00 0.91 0.97 17.68 Hide/expose window via popup (50 kids) + 17.29 1.01 1.00 1.01 17.07 Hide/expose window via popup (75 kids) + 16.74 1.00 1.00 1.00 16.17 Hide/expose window via popup (100 kids) + 10.30 1.00 1.00 1.00 10.51 Hide/expose window via popup (200 kids) + 16.48 1.01 1.00 1.00 26.05 Move window (4 kids) + 17.01 0.95 1.00 1.00 23.97 Move window (16 kids) + 16.95 1.00 1.00 1.00 22.90 Move window (25 kids) + 16.05 1.01 1.00 1.00 21.32 Move window (50 kids) + 15.58 1.00 0.98 0.98 19.44 Move window (75 kids) + 14.98 1.02 1.03 1.03 18.17 Move window (100 kids) + 10.90 1.01 1.01 1.00 12.68 Move window (200 kids) + 49.42 1.00 1.00 1.00 198.27 Moved unmapped window (4 kids) + 50.72 0.97 1.00 1.00 193.66 Moved unmapped window (16 kids) + 50.87 1.00 0.99 1.00 195.09 Moved unmapped window (25 kids) + 50.72 1.00 1.00 1.00 189.34 Moved unmapped window (50 kids) + 50.87 1.00 1.00 1.00 191.33 Moved unmapped window (75 kids) + 50.87 1.00 1.00 0.90 186.71 Moved unmapped window (100 kids) + 50.87 1.00 1.00 1.00 179.19 Moved unmapped window (200 kids) + 41.04 1.00 1.00 1.00 56.61 Move window via parent (4 kids) + 69.81 1.00 1.00 1.00 130.82 Move window via parent (16 kids) + 95.81 1.00 1.00 1.00 141.92 Move window via parent (25 kids) + 95.98 1.00 1.00 1.00 149.43 Move window via parent (50 kids) + 96.59 1.01 1.01 1.00 153.98 Move window via parent (75 kids) + 97.19 1.00 1.00 1.00 157.30 Move window via parent (100 kids) + 96.67 1.00 0.99 0.96 159.44 Move window via parent (200 kids) + 17.75 1.01 1.00 1.00 27.61 Resize window (4 kids) + 17.94 1.00 1.00 0.99 25.42 Resize window (16 kids) + 17.92 1.01 1.00 1.00 24.47 Resize window (25 kids) + 17.24 0.97 1.00 1.00 24.14 Resize window (50 kids) + 16.81 1.00 1.00 0.99 22.75 Resize window (75 kids) + 16.08 1.00 1.00 1.00 21.20 Resize window (100 kids) + 12.92 1.00 0.99 1.00 16.26 Resize window (200 kids) + 52.94 1.01 1.00 1.00 327.12 Resize unmapped window (4 kids) + 53.60 1.01 1.01 1.01 333.71 Resize unmapped window (16 kids) + 52.99 1.00 1.00 1.00 337.29 Resize unmapped window (25 kids) + 51.98 1.00 1.00 1.00 329.38 Resize unmapped window (50 kids) + 53.05 0.89 1.00 1.00 322.60 Resize unmapped window (75 kids) + 53.05 1.00 1.00 1.00 318.08 Resize unmapped window (100 kids) + 53.11 1.00 1.00 0.99 306.21 Resize unmapped window (200 kids) + 16.76 1.00 0.96 1.00 19.46 Circulate window (4 kids) + 17.24 1.00 1.00 0.97 16.24 Circulate window (16 kids) + 16.30 1.03 1.03 1.03 15.85 Circulate window (25 kids) + 13.45 1.00 1.00 1.00 14.90 Circulate window (50 kids) + 12.91 1.00 1.00 1.00 13.06 Circulate window (75 kids) + 11.30 0.98 1.00 1.00 11.03 Circulate window (100 kids) + 7.58 1.01 1.01 0.99 7.47 Circulate window (200 kids) + 1.01 1.01 0.98 1.00 0.95 Circulate Unmapped window (4 kids) + 1.07 1.07 1.01 1.07 1.02 Circulate Unmapped window (16 kids) + 1.04 1.09 1.06 1.05 0.97 Circulate Unmapped window (25 kids) + 1.04 1.23 1.20 1.18 1.05 Circulate Unmapped window (50 kids) + 1.18 1.53 1.19 1.45 1.24 Circulate Unmapped window (75 kids) + 1.08 1.02 1.01 1.74 1.01 Circulate Unmapped window (100 kids) + 1.01 1.12 0.98 0.91 0.97 Circulate Unmapped window (200 kids) + + + + + +Profiling with OProfile + +OProfile (available from http://oprofile.sourceforge.net/) is a +system-wide profiler for Linux systems that uses processor-level +counters to collect sampling data. OProfile can provide information +that is similar to that provided by gprof, but without the +necessity of recompiling the program with special instrumentation (i.e., +OProfile can collect statistical profiling information about optimized +programs). A test harness was developed to collect OProfile data for +each x11perf test individually. + + +Test runs were performed using the RETIRED_INSNS counter on the AMD +Athlon and the CPU_CLK_HALTED counter on the Intel Pentium III (with a +test configuration different from the one described above). We have +examined OProfile output and have compared it with gprof output. +This investigation has not produced results that yield performance +increases in x11perf numbers. + + + + + + + + + +X Test Suite + +The X Test Suite was run on the fully optimized DMX server using the +configuration described above. The following failures were noted: + +XListPixmapFormats: Test 1 [1] +XChangeWindowAttributes: Test 32 [1] +XCreateWindow: Test 30 [1] +XFreeColors: Test 4 [3] +XCopyArea: Test 13, 17, 21, 25, 30 [2] +XCopyPlane: Test 11, 15, 27, 31 [2] +XSetFontPath: Test 4 [1] +XChangeKeyboardControl: Test 9, 10 [1] + +[1] Previously documented errors expected from the Xinerama + implementation (see Phase I discussion). +[2] Newly noted errors that have been verified as expected + behavior of the Xinerama implementation. +[3] Newly noted error that has been verified as a Xinerama + implementation bug. + + + + + + + + + +Phase III + +During the third phase of development, support was provided for the +following extensions: SHAPE, RENDER, XKEYBOARD, XInput. + + + +SHAPE + +The SHAPE extension is supported. Test applications (e.g., xeyes and +oclock) and window managers that make use of the SHAPE extension will +work as expected. + + + + +RENDER + +The RENDER extension is supported. The version included in the DMX +CVS tree is version 0.2, and this version is fully supported by Xdmx. +Applications using only version 0.2 functions will work correctly; +however, some apps that make use of functions from later versions do not +properly check the extension's major/minor version numbers. These apps +will fail with a Bad Implementation error when using post-version 0.2 +functions. This is expected behavior. When the DMX CVS tree is updated +to include newer versions of RENDER, support for these newer functions +will be added to the DMX X server. + + + + +XKEYBOARD + +The XKEYBOARD extension is supported. If present on the back-end X +servers, the XKEYBOARD extension will be used to obtain information +about the type of the keyboard for initialization. Otherwise, the +keyboard will be initialized using defaults. Note that this departs +from older behavior: when Xdmx is compiled without XKEYBOARD support, +the map from the back-end X server will be preserved. With XKEYBOARD +support, the map is not preserved because better information and control +of the keyboard is available. + + + + +XInput + +The XInput extension is supported. Any device can be used as a core +device and be used as an XInput extension device, with the exception of +core devices on the back-end servers. This limitation is present +because cursor handling on the back-end requires that the back-end +cursor sometimes track the Xdmx core cursor -- behavior that is +incompatible with using the back-end pointer as a non-core device. + + +Currently, back-end extension devices are not available as Xdmx +extension devices, but this limitation should be removed in the future. + + +To demonstrate the XInput extension, and to provide more examples for +low-level input device driver writers, USB device drivers have been +written for mice (usb-mou), keyboards (usb-kbd), and +non-mouse/non-keyboard USB devices (usb-oth). Please see the man page +for information on Linux kernel drivers that are required for using +these Xdmx drivers. + + + + +DPMS + +The DPMS extension is exported but does not do anything at this time. + + + + + +Other Extensions + +The LBX, + SECURITY, + XC-APPGROUP, and + XFree86-Bigfont +extensions do not require any special Xdmx support and have been exported. + + +The + BIG-REQUESTS, + DEC-XTRAP, + DOUBLE-BUFFER, + Extended-Visual-Information, + FontCache, + GLX, + MIT-SCREEN-SAVER, + MIT-SHM, + MIT-SUNDRY-NONSTANDARD, + RECORD, + SECURITY, + SGI-GLX, + SYNC, + TOG-CUP, + X-Resource, + XC-MISC, + XFree86-DGA, + XFree86-DRI, + XFree86-Misc, + XFree86-VidModeExtension, and + XVideo +extensions are not supported at this time, but will be evaluated +for inclusion in future DMX releases. See below for additional work +on extensions after Phase III. + + + + + +Phase IV + + +Moving to XFree86 4.3.0 + +For Phase IV, the recent release of XFree86 4.3.0 (27 February 2003) +was merged onto the dmx.sourceforge.net CVS trunk and all work is +proceeding using this tree. + + + + +Extensions + + +XC-MISC (supported) + +XC-MISC is used internally by the X library to recycle XIDs from the +X server. This is important for long-running X server sessions. Xdmx +supports this extension. The X Test Suite passed and failed the exact +same tests before and after this extension was enabled. + + + + + +Extended-Visual-Information (supported) + +The Extended-Visual-Information extension provides a method for an X +client to obtain detailed visual information. Xdmx supports this +extension. It was tested using the hw/dmx/examples/evi example +program. Note that this extension is not Xinerama-aware -- it will +return visual information for each screen even though Xinerama is +causing the X server to export a single logical screen. + + + + + +RES (supported) + +The X-Resource extension provides a mechanism for a client to obtain +detailed information about the resources used by other clients. This +extension was tested with the hw/dmx/examples/res program. The +X Test Suite passed and failed the exact same tests before and after +this extension was enabled. + + + + + +BIG-REQUESTS (supported) + +This extension enables the X11 protocol to handle requests longer +than 262140 bytes. The X Test Suite passed and failed the exact same +tests before and after this extension was enabled. + + + + + +XSYNC (supported) + +This extension provides facilities for two different X clients to +synchronize their requests. This extension was minimally tested with +xdpyinfo and the X Test Suite passed and failed the exact same +tests before and after this extension was enabled. + + + + + +XTEST, RECORD, DEC-XTRAP (supported) and XTestExtension1 (not supported) + +The XTEST and RECORD extension were developed by the X Consortium for +use in the X Test Suite and are supported as a standard in the X11R6 +tree. They are also supported in Xdmx. When X Test Suite tests that +make use of the XTEST extension are run, Xdmx passes and fails exactly +the same tests as does a standard XFree86 X server. When the +rcrdtest test (a part of the X Test Suite that verifies the RECORD +extension) is run, Xdmx passes and fails exactly the same tests as does +a standard XFree86 X server. + + +There are two older XTEST-like extensions: DEC-XTRAP and +XTestExtension1. The XTestExtension1 extension was developed for use by +the X Testing Consortium for use with a test suite that eventually +became (part of?) the X Test Suite. Unlike XTEST, which only allows +events to be sent to the server, the XTestExtension1 extension also +allowed events to be recorded (similar to the RECORD extension). The +second is the DEC-XTRAP extension that was developed by the Digital +Equipment Corporation. + + +The DEC-XTRAP extension is available from Xdmx and has been tested +with the xtrap* tools which are distributed as standard X11R6 +clients. + + +The XTestExtension1 is not supported because it does not appear +to be used by any modern X clients (the few that support it also support +XTEST) and because there are no good methods available for testing that +it functions correctly (unlike XTEST and DEC-XTRAP, the code for +XTestExtension1 is not part of the standard X server source tree, so +additional testing is important). + + +Most of these extensions are documented in the X11R6 source tree. +Further, several original papers exist that this author was unable to +locate -- for completeness and historical interest, citations are +provide: + + +XRECORD + +Martha Zimet. Extending X For Recording. 8th Annual X +Technical Conference Boston, MA January 24-26, 1994. + + +DEC-XTRAP + +Dick Annicchiarico, Robert Chesler, Alan Jamison. XTrap +Architecture. Digital Equipment Corporation, July 1991. + + +XTestExtension1 + +Larry Woestman. X11 Input Synthesis Extension +Proposal. Hewlett Packard, November 1991. + + + + + + +MIT-MISC (not supported) + +The MIT-MISC extension is used to control a bug-compatibility flag +that provides compatibility with xterm programs from X11R1 and X11R2. +There does not appear to be a single client available that makes use of +this extension and there is not way to verify that it works correctly. +The Xdmx server does not support MIT-MISC. + + + + +SCREENSAVER (not supported) + +This extension provides special support for the X screen saver. It +was tested with beforelight, which appears to be the only client that +works with it. When Xinerama was not active, beforelight behaved +as expected. However, when Xinerama was active, beforelight did +not behave as expected. Further, when this extension is not active, +xscreensaver (a widely-used X screen saver program) did not behave +as expected. Since this extension is not Xinerama-aware and is not +commonly used with expected results by clients, we have left this +extension disabled at this time. + + + + +GLX (supported) + +The GLX extension provides OpenGL and GLX windowing support. In +Xdmx, the extension is called glxProxy, and it is Xinerama aware. It +works by either feeding requests forward through Xdmx to each of the +back-end servers or handling them locally. All rendering requests are +handled on the back-end X servers. This code was donated to the DMX +project by SGI. For the X Test Suite results comparison, see below. + + + + +RENDER (supported) + +The X Rendering Extension (RENDER) provides support for digital image +composition. Geometric and text rendering are supported. RENDER is +partially Xinerama-aware, with text and the most basic compositing +operator; however, its higher level primitives (triangles, triangle +strips, and triangle fans) are not yet Xinerama-aware. The RENDER +extension is still under development, and is currently at version 0.8. +Additional support will be required in DMX as more primitives and/or +requests are added to the extension. + + +There is currently no test suite for the X Rendering Extension; +however, there has been discussion of developing a test suite as the +extension matures. When that test suite becomes available, additional +testing can be performed with Xdmx. The X Test Suite passed and failed +the exact same tests before and after this extension was enabled. + + + + +Summary + + +To summarize, the following extensions are currently supported: + BIG-REQUESTS, + DEC-XTRAP, + DMX, + DPMS, + Extended-Visual-Information, + GLX, + LBX, + RECORD, + RENDER, + SECURITY, + SHAPE, + SYNC, + X-Resource, + XC-APPGROUP, + XC-MISC, + XFree86-Bigfont, + XINERAMA, + XInputExtension, + XKEYBOARD, and + XTEST. + + +The following extensions are not supported at this time: + DOUBLE-BUFFER, + FontCache, + MIT-SCREEN-SAVER, + MIT-SHM, + MIT-SUNDRY-NONSTANDARD, + TOG-CUP, + XFree86-DGA, + XFree86-Misc, + XFree86-VidModeExtension, + XTestExtensionExt1, and + XVideo. + + + + + +Additional Testing with the X Test Suite + + +XFree86 without XTEST + +After the release of XFree86 4.3.0, we retested the XFree86 X server +with and without using the XTEST extension. When the XTEST extension +was not used for testing, the XFree86 4.3.0 server running on our +usual test system with a Radeon VE card reported unexpected failures in +the following tests: + +XListPixmapFormats: Test 1 +XChangeKeyboardControl: Tests 9, 10 +XGetDefault: Test 5 +XRebindKeysym: Test 1 + + + + + +XFree86 with XTEST + +When using the XTEST extension, the XFree86 4.3.0 server reported the +following errors: + +XListPixmapFormats: Test 1 +XChangeKeyboardControl: Tests 9, 10 +XGetDefault: Test 5 +XRebindKeysym: Test 1 + +XAllowEvents: Tests 20, 21, 24 +XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 +XGrabKey: Test 8 +XSetPointerMapping: Test 3 +XUngrabButton: Test 4 + + + +While these errors may be important, they will probably be fixed +eventually in the XFree86 source tree. We are particularly interested +in demonstrating that the Xdmx server does not introduce additional +failures that are not known Xinerama failures. + + + + +Xdmx with XTEST, without Xinerama, without GLX + +Without Xinerama, but using the XTEST extension, the following errors +were reported from Xdmx (note that these are the same as for the XFree86 +4.3.0, except that XGetDefault no longer fails): + +XListPixmapFormats: Test 1 +XChangeKeyboardControl: Tests 9, 10 +XRebindKeysym: Test 1 + +XAllowEvents: Tests 20, 21, 24 +XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 +XGrabKey: Test 8 +XSetPointerMapping: Test 3 +XUngrabButton: Test 4 + + + + + +Xdmx with XTEST, with Xinerama, without GLX + +With Xinerama, using the XTEST extension, the following errors +were reported from Xdmx: + +XListPixmapFormats: Test 1 +XChangeKeyboardControl: Tests 9, 10 +XRebindKeysym: Test 1 + +XAllowEvents: Tests 20, 21, 24 +XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 +XGrabKey: Test 8 +XSetPointerMapping: Test 3 +XUngrabButton: Test 4 + +XCopyPlane: Tests 13, 22, 31 (well-known XTEST/Xinerama interaction issue) +XDrawLine: Test 67 +XDrawLines: Test 91 +XDrawSegments: Test 68 + +Note that the first two sets of errors are the same as for the XFree86 +4.3.0 server, and that the XCopyPlane error is a well-known error +resulting from an XTEST/Xinerama interaction when the request crosses a +screen boundary. The XDraw* errors are resolved when the tests are run +individually and they do not cross a screen boundary. We will +investigate these errors further to determine their cause. + + + + +Xdmx with XTEST, with Xinerama, with GLX + +With GLX enabled, using the XTEST extension, the following errors +were reported from Xdmx (these results are from early during the Phase +IV development, but were confirmed with a late Phase IV snapshot): + +XListPixmapFormats: Test 1 +XChangeKeyboardControl: Tests 9, 10 +XRebindKeysym: Test 1 + +XAllowEvents: Tests 20, 21, 24 +XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25 +XGrabKey: Test 8 +XSetPointerMapping: Test 3 +XUngrabButton: Test 4 + +XClearArea: Test 8 +XCopyArea: Tests 4, 5, 11, 14, 17, 23, 25, 27, 30 +XCopyPlane: Tests 6, 7, 10, 19, 22, 31 +XDrawArcs: Tests 89, 100, 102 +XDrawLine: Test 67 +XDrawSegments: Test 68 + +Note that the first two sets of errors are the same as for the XFree86 +4.3.0 server, and that the third set has different failures than when +Xdmx does not include GLX support. Since the GLX extension adds new +visuals to support GLX's visual configs and the X Test Suite runs tests +over the entire set of visuals, additional rendering tests were run and +presumably more of them crossed a screen boundary. This conclusion is +supported by the fact that nearly all of the rendering errors reported +are resolved when the tests are run individually and they do no cross a +screen boundary. + + +Further, when hardware rendering is disabled on the back-end displays, +many of the errors in the third set are eliminated, leaving only: + +XClearArea: Test 8 +XCopyArea: Test 4, 5, 11, 14, 17, 23, 25, 27, 30 +XCopyPlane: Test 6, 7, 10, 19, 22, 31 + + + + + +Conclusion + +We conclude that all of the X Test Suite errors reported for Xdmx are +the result of errors in the back-end X server or the Xinerama +implementation. Further, all of these errors that can be reasonably +fixed at the Xdmx layer have been. (Where appropriate, we have +submitted patches to the XFree86 and Xinerama upstream maintainers.) + + + + + +Dynamic Reconfiguration + +During this development phase, dynamic reconfiguration support was +added to DMX. This support allows an application to change the position +and offset of a back-end server's screen. For example, if the +application would like to shift a screen slightly to the left, it could +query Xdmx for the screen's <x,y> position and then dynamically +reconfigure that screen to be at position <x+10,y>. When a screen +is dynamically reconfigured, input handling and a screen's root window +dimensions are adjusted as needed. These adjustments are transparent to +the user. + + + +Dynamic reconfiguration extension + +The application interface to DMX's dynamic reconfiguration is through +a function in the DMX extension library: + +Bool DMXReconfigureScreen(Display *dpy, int screen, int x, int y) + +where dpy is DMX server's display, screen is the number of the +screen to be reconfigured, and x and y are the new upper, +left-hand coordinates of the screen to be reconfigured. + + +The coordinates are not limited other than as required by the X +protocol, which limits all coordinates to a signed 16 bit number. In +addition, all coordinates within a screen must also be legal values. +Therefore, setting a screen's upper, left-hand coordinates such that the +right or bottom edges of the screen is greater than 32,767 is illegal. + + + + +Bounding box + +When the Xdmx server is started, a bounding box is calculated from +the screens' layout given either on the command line or in the +configuration file. This bounding box is currently fixed for the +lifetime of the Xdmx server. + + +While it is possible to move a screen outside of the bounding box, it +is currently not possible to change the dimensions of the bounding box. +For example, it is possible to specify coordinates of <-100,-100> +for the upper, left-hand corner of the bounding box, which was +previously at coordinates <0,0>. As expected, the screen is moved +down and to the right; however, since the bounding box is fixed, the +left side and upper portions of the screen exposed by the +reconfiguration are no longer accessible on that screen. Those +inaccessible regions are filled with black. + + +This fixed bounding box limitation will be addressed in a future +development phase. + + + + +Sample applications + +An example of where this extension is useful is in setting up a video +wall. It is not always possible to get everything perfectly aligned, +and sometimes the positions are changed (e.g., someone might bump into a +projector). Instead of physically moving projectors or monitors, it is +now possible to adjust the positions of the back-end server's screens +using the dynamic reconfiguration support in DMX. + + +Other applications, such as automatic setup and calibration tools, +can make use of dynamic reconfiguration to correct for projector +alignment problems, as long as the projectors are still arranged +rectilinearly. Horizontal and vertical keystone correction could be +applied to projectors to correct for non-rectilinear alignment problems; +however, this must be done external to Xdmx. + + +A sample test program is included in the DMX server's examples +directory to demonstrate the interface and how an application might use +dynamic reconfiguration. See dmxreconfig.c for details. + + + + +Additional notes + +In the original development plan, Phase IV was primarily devoted to +adding OpenGL support to DMX; however, SGI became interested in the DMX +project and developed code to support OpenGL/GLX. This code was later +donated to the DMX project and integrated into the DMX code base, which +freed the DMX developers to concentrate on dynamic reconfiguration (as +described above). + + + + + +Doxygen documentation + +Doxygen is an open-source (GPL) documentation system for generating +browseable documentation from stylized comments in the source code. We +have placed all of the Xdmx server and DMX protocol source code files +under Doxygen so that comprehensive documentation for the Xdmx source +code is available in an easily browseable format. + + + + +Valgrind + +Valgrind, an open-source (GPL) memory debugger for Linux, was used to +search for memory management errors. Several memory leaks were detected +and repaired. The following errors were not addressed: + + + When the X11 transport layer sends a reply to the client, only + those fields that are required by the protocol are filled in -- + unused fields are left as uninitialized memory and are therefore + noted by valgrind. These instances are not errors and were not + repaired. + + + At each server generation, glxInitVisuals allocates memory that + is never freed. The amount of memory lost each generation + approximately equal to 128 bytes for each back-end visual. + Because the code involved is automatically generated, this bug + has not been fixed and will be referred to SGI. + + + At each server generation, dmxRealizeFont calls XLoadQueryFont, + which allocates a font structure that is not freed. + dmxUnrealizeFont can free the font structure for the first + screen, but cannot free it for the other screens since they are + already closed by the time dmxUnrealizeFont could free them. + The amount of memory lost each generation is approximately equal + to 80 bytes per font per back-end. When this bug is fixed in + the the X server's device-independent (dix) code, DMX will be + able to properly free the memory allocated by XLoadQueryFont. + + + + + + +RATS + +RATS (Rough Auditing Tool for Security) is an open-source (GPL) +security analysis tool that scans source code for common +security-related programming errors (e.g., buffer overflows and TOCTOU +races). RATS was used to audit all of the code in the hw/dmx directory +and all "High" notations were checked manually. The code was either +re-written to eliminate the warning, or a comment containing "RATS" was +inserted on the line to indicate that a human had checked the code. +Unrepaired warnings are as follows: + + + Fixed-size buffers are used in many areas, but code has been + added to protect against buffer overflows (e.g., XmuSnprint). + The only instances that have not yet been fixed are in + config/xdmxconfig.c (which is not part of the Xdmx server) and + input/usb-common.c. + + + vprintf and vfprintf are used in the logging routines. In + general, all uses of these functions (e.g., dmxLog) provide a + constant format string from a trusted source, so the use is + relatively benign. + + + glxProxy/glxscreens.c uses getenv and strcat. The use of these + functions is safe and will remain safe as long as + ExtensionsString is longer then GLXServerExtensions (ensuring + this may not be ovious to the casual programmer, but this is in + automatically generated code, so we hope that the generator + enforces this constraint). + + + + + + + + + + + + + +
+ + + + diff --git a/xorg-server/hw/dmx/doc/scaled.sgml b/xorg-server/hw/dmx/doc/scaled.sgml deleted file mode 100644 index 6b8ee413f..000000000 --- a/xorg-server/hw/dmx/doc/scaled.sgml +++ /dev/null @@ -1,707 +0,0 @@ - -
- - - Scaled Window Support in DMX - Rickard E. Faith and Kevin E. Martin - 15 October 2003 (created 19 September 2003) - - This document investigates the possibility of adding scaled window - support to the DMX X server, thereby allowing a window or some - selected part of the logical DMX area to be displayed using a - scaling factor. For example, this might allow the contents of a - window to be magnified for easier viewing. In particular, scaling - for the VNC client is explored. Copyright 2003 - by Red Hat, Inc., Raleigh, North Carolina - - - - - - - Introduction - DMX -

- The DMX X server (Xdmx) is a proxy server that is designed - to allow X servers on multiple machines to be combined into - a single multi-headed X server. Combined with Xinerama, - these heads can appear as a single very high-resolution - screen. Typical applications include the creation of a - video wall with 16 1280x1024 displays arranged in a - rectangle, for a total resolution of of 5120x4096. -

- - Problem Statement -

- Applications displayed on a physically large video wall that - provides high pixel-resolution may be difficult to see, - especially if the application is designed for use on a - typical desktop computer with a relatively small display - located close to the human operator. The goal of this paper - is to describe and discuss solutions to this problem. -

-

- The original driving problem for this work is to provide - scaling for the vncviewer application when - displayed using DMX (VNC scaling is currently available only - with the Windows client, and there is no plan to extend that - capability to other clients). While this specific problem - will be addressed in this paper, the general solution space - will also be explored, since this may lead to a good - solution not only for vncviewer but also for - other applications. -

- - Task -

- For reference, here is the original description of the task - this paper addresses: - - Scaled window support (for VNC) - - - Investigate possibility of implementing a "scaled - window" extension: - - - Add XCreateScaledWindow call that could be used - in place of XCreateWindow - - - All primitives drawn to scaled window would be - scaled by appropriate (integral?) scaling factor - - - - - Alternate approach: special case VNC support - - - - -

- - - - Previous Work -

- This section reviews relevant previous work. -

- VNC - Scaling under VNC -

- When using the vncviewer program for Windows, it - is possible to specify a scaling factor (as numerator and - denominator). When scaling is in effect, the viewer - software uses StretchBlt (instead of BitBlt) to display - the pixels for the user. When this call is made, the - viewer already has received all of the pixel information - (at full unscaled resolution). -

-

- The scaling in VNC is primitive. It does not conserve - bandwidth, it does not treat textual information - differently (i.e., by using a suitably scaled font), and - it does not provide any anti-aliasing other than that - provided by the underlying (Windows-only) system library. -

- - - The X Video Extension -

- The X Video Extension is a widely-available extension to the - X11 protocol that provides support for streaming video. - Integral to this support is the ability to arbitrarily scale - the output. In version 2.2 of the X Video specification, - support for scaled still images was provided, using both - shared memory and traditional transport. The API for this - support uses calls that are quite similar to XCreateWindow, - XPutImage, and XShmPutImage. Currently, most of the drivers - implemented in XFree86 only support data in various YUV - formats. However, several modern video adaptors support RGB - as well. -

-

- Note, though, that the target output for this scaling is an - overlay plane -- so X Video provides functionality that is - fundamentally different from that provided by the Windows - StrechBlt call. -

- - - - Possible Solutions -

- This section briefly discusses possible solutions, including - major advantages and disadvantages from both the - implementation and the end-user programmer standpoint. -

- VNC-like Scaling - Software Scaling -

- The vncviewer application could be modified to - provide software scaling. This is not a general solution, - but it does solve one of the goals of this work. -

-

- A prototype of this solution was implemented and a patch - against vnc-3.3.7-unixsrc is available in the - dmx/external directory. Because of limited time - available for this work, all of the edge cases were not - considered and the solution works well mainly for integer - scaling. -

-

- Currently, vncviewer writes to the X display - with XPutImage, XCopyArea, and XFillRectangle. All - instances of these calls have to be aware of scaling - and must round correctly. In the prototype solution, - rounding is incorrect and can cause artifacts. -

-

- A better solution would be to cache all updates to the - desktop image in vncviewer and only send the - damaged area to the X display with XPutImage. This would - allow the damaged area to be computed so that rounding - errors do not create artifacts. This method is probably - similar to what is used in the Window client. (The whole - VNC suite is being re-written in C++ and the forthcoming - version 4 has not been evaluated.) -

- - Scaling with the X Video Extension -

- The scaling in the Windows vncviewer application - makes use of a scaled blit that is supplied by the - underlying system library. Several video cards currently - provide support for a scaled blit, and some X servers - (including XFree86) expose this capability to applications - via the XvPutImage interface of the X Video Extension. - The capability exposed by XvPutImage results in the scaled - image being drawn to an overlay plane. Most video cards - also provide support for a scaled blit into the normal - output planes, but this is not exposed via XvPutImage. -

-

- The vncviewer program could be modified to use - the X Video Extension to provide scaling under X11 that is - similar to the scaling currently provided under Windows. - Unfortunately, Xdmx does not currently export the X Video - Extension, so this would not provide an immediate solution - usable with DMX. -

-

- A very early-stage proof-of-concept prototype was - implemented and a preliminary patch against - vnc-3.3.7-unixsrc is available in the - dmx/external directory. This prototype was - implemented to better understand the problems that must be - solved to make this solution viable: - - - As noted under the software scaling section above, - vncviewer writes to the X display with - several different calls. These calls write to the - normal output planes and are compatible with - XvPutImage, which writes to an overlay plane. To - eliminate artifacts caused by this problem, - vncviewer should be modified so that a cached - copy of the desktop is available, either as a - client-side image or a server-side off-screen pixmap, - so that XvPutImage would be the only method for - writing to the X display. - - -

- Although several modern graphics adaptors support - hardware scaling using an RGB format (e.g., ATI - Radeon, nVidia, etc.), XFree86 drivers typically - only implement YUV formats. YUV generally compress - the pixel information in some way. For example, two - commonly implemented formats, YUY2 and UYVY provide - intensity information for every RGB pixel, but only - provide chroma and luminance information for pairs - of horizontal pixels. Since VNC uses - pixel-resolution for communicating updates on the - wire, additional artifacts are introduced (because - there may not be enough information from the wire to - update a pair of pixels). -

- Further, the well-known problem with YUV encoding - is even more evident when the image is a desktop - instead of a movie. For example, consider a - 1-pixel-wide vertical window border. If the border - changes in color but not intensity (e.g., because a - window manager uses color to indicate focus), there - may or may not be a change in the YUY2 image, - depending on the algorithm used for RGB to YUV - conversion and on how the border pixel is ordered in - the pair of pixels used by the algorithm. -

- Many of these artifacts could be eliminated if - vncviewer cached a complete RGB image of - the desktop, and only did the conversion to YUV for - properly aligned areas of damage. The remaining artifacts - could be eliminated if an RGB format was used with X - Video (which may require the extension of existing - XFree86 drivers to support RGB). - - - Most modern video cards support exactly one overlay - plane that is suitable for use with X Video. - Therefore, only one application can use X Video at any - given time. This is a severe limitation in a desktop - environment. - - -

- Implementing the X Video Extension for DMX -

- The user-level API for X Video is fairly simple, but the - underlying support required for the full specification - is large. However, since the API provides a method to - query supported capabilities, a usable subset of X - Video can be implemented that would support XvPutImage - and little else. This would require support for the - following: - - - X Video Extension API calls, including the - following: - - XvQueryExtension - XvQueryAdaptors - XvQueryPortAttributes - XvFreeAdaptorInfo - XvListImageFormats - XvGrabPort - XvCreateImage - XvPutImage - XvShmCreateImage - XvShmPutImage - - - - Support for querying back-end X Video Extension - capabilities. - - - Support for sending the image to the back-ends. - Because X Video requires sending full images, there - may be a trade-off between bandwidth limitations and - additional complexity to divide the image up such - that is scales properly. - - - Possible support for a software fall-back. For - example, if all of the back-ends do not support the X - Video Extension, software scaling can be implemented - such that the image is sent to the back-end with - XPutImage. This pathway would have poor - performance. - - -

- - Supporting RGB formats for the X Video Extension -

- Assuming an XFree86 driver already supports the X Video - Extension, and assuming the target hardware supports an - RGB format, then adding support for that format is - relatively simple and straightforward. -

- - - Scaling with an XPutImageScaled Extension -

- Instead of (or in addition to) implementing the X Video - Extension in DMX, one obvious solution would be to - implement a new extension that provides access to - hardware-assisted scaled blits, similar to the StretchBlt - call available under Windows. This call would scale RGB - images and would not use the overlay plane (unlike the X - Video Extension). -

-

- This approach has many of the same advantages and - disadvantages as the XCopyAreaScaled Extension, discussed - in the next section. Discussion of XPutImageScaled is - deferred in favor of XCopyAreaScaled for the following - reasons: - - - XPutImageScaled can be emulated with XCopyAreaScaled - by first using XPutImage to copy the image to an - off-screen pixmap, and then calling XCopyAreaScaled - between that off-screen pixmap and the target - drawable. - - - Since XCopyAreaScaled would copy between two areas of - on-screen or off-screen memory, it has additional uses - and can be viewed as efficiently providing a superset - of XPutImageScaled functionality. - - -

- - Scaling with an XCopyAreaScaled Extension -

- As noted in the previous section, because XCopyAreaScaled - provides a superset of the functionality provided by - XPutImageScaled, we will consider this extension instead. -

-

- First, XCopyAreaScaled would provide for RGB scaling - between pixmaps (i.e., on-screen or off-screen areas of - memory that reside on the video card). Unlike the X Video - Extension, which writes into an overlay plane, - XCopyAreaScaled would write into the non-overlay areas of - the screen. Key points to consider are as follows: - - - Because different planes are involved, the two scaling - operations are usually implemented in hardware - differently, so an XCopyAreaScaled extension could be - added in a manner that would neither conflict with nor - interact with the X Video extension in any way. - - - The XCopyAreaScaled extension provides new - functionality that the X Video Extension does not - provide. Based on anecdotal feedback, we believe that - many people outside the DMX and VNC communities would - be excited about this extension. - - - The main drawback to this extension is that it is new - and needs to be implemented at the driver level in - XFree86 for each video card to be supported. At the - present time, it is more likely that the X Video - Extension will be implemented for a particular piece - hardware because the X Video extension has multimedia - uses. However, over time, we would expect the - XCopyAreaScaled extension to be implemented along with - the X Video extension, especially if it becomes - popular. - - - Another drawback is that not all modern cards provide - support for a simple scaled blit operation. However, - these cards usually do provide a 3D pipeline which - could be used to provide this functionality in a - manner that is transparent to the client application - that is using the XCopyAreaScaled extension. However, - this implementation pathway would make this extension - somewhat more difficult to implement on certain cards. - - -

- - Scaling with OpenGL -

- Another general solution to the scaling problem is to use - the texture scaling found in all 3D hardware. This - ability is already exposed through OpenGL and can be - exploited by clients without X server modification (i.e., - other than the ability to support OpenGL). An application - using OpenGL would transmit the non-scaled image to the X - server as a texture, and would then display a single - non-transformed rect using that texture. This also works - around the single overlay problem with the X Video - Extension as well as the need to implement additional - scaled primitive extensions. -

-

- The downside is that most OpenGL implementations require - power of 2 texture sizes and this can be very wasteful of - memory if, for example, the application needs to scale a - 1025x1025 image, which would require a 2048x2048 texture - area (even a 640x480 image would require a 1024x512 - texture). Another downside is that some OpenGL - implementations have a limited about of texture memory and - cannot handle textures that are very large. For example, - they might limit the texture size to 1024x1024. -

- - - Application-transparent Scaling for DMX - Back-end Scaling Without Disconnect/Reconnect -

- VNC does scaling on the client side (in the - vncviewer application). Implementing a similar - solution for DMX would require support in the back-end X - servers and, therefore, is not a general solution. -

-

- XFree86 already implements some support for "scaling" that - could be used with DMX: if, in the XF86Config file, - multiple Modes are listed in the Display Subsection of the - Screen Section, then pressing Ctrl-Alt-Plus and - Ctrl-Alt-Minus can be used to iterate through the listed - modes. The display dimensions will change to the - dimensions in the Modes line, but the logical dimensions - of the X server (i.e., the dimensions that Xdmx knows - about) will not change. -

-

- Further, the dimensions of the XFree86 display are under - software control (via the XFree86-VidModeExtension), so - the Xdmx server could change the screen dimensions on a - per-display basis, thereby scaling the information on part - of that display. -

-

- However, this scaling appears to have limited use. For - example, assume a 4 by 4 display wall consisting of 16 - 1280x1024 displays. If all of the back-end servers were - simultaneously configured to display 640x480, the left - hand corner of each display would be magnified, but the - composite result would be unreadable. Magnifying one - display at a time could be usable, but could have limited - utility, since the result would still be no larger than a - single display. -

- - Back-end Scaling With Disconnect/Reconnect -

- Disconnect and reconnect features are not currently - supported in DMX, but are scheduled to be implemented in - the future. These features, combined with the - XFree86-VidModeExtension Extension, would allow an - application to do the following: - - - Disconnect a specific back-end server (via the DMX - Extension), - - - reconfigure the XFree86 back-end server resolution, - and - - - reconnect the back-end server to DMX -- at a new - origin with the new screen resolution. - - -

-

- For example, consider a display wall consisting of 16 - 1280x1024 displays with a total resolution of 5120x4096. - All of the screens could be disconnected, repositioned, - and reconnected each at a resolution of 640x480. The - total resolution of the display wall would be 2560x1920, - allowing a view of a selected area approximately - one-fourth of the size of the DMX display. This change - would be completely application independent (except, - perhaps, for a DMX-aware window manager). When work at - the increased resolution was completed, the back-end - servers could be disconnected, reconfigured, and - reconnected for the original 5120x4096 view. -

-

- Support for this type of scaling can be implemented in a - DMX-aware X11 client assuming the DMX server support - arbitrary disconnect and reconnect semantics. Because - this application cannot be written before - disconnect/reconnect is implemented, this solution will - not be discussed further in this paper. -

- - Server-side Scaling -

- In earlier versions of DMX, a frame buffer was maintained - on the server side, and XPutImage was used to move the - information from the server to the client (similar to some - early VNC implementations). The use of a server-side - frame buffer would allow the server to do scaling, but is - not a recommended solution because of overall performance - issues and server-side memory issues (i.e., the frame - buffer would be very large for large display walls). -

-

- Exploration of this path is not recommended. -

- - - XCreateScaledWindow API -

- The implementation of X Video Extension in DMX, and the use - of XvPutImage by applications requiring scaling requires - significant changes in DMX Further, XvPutImage is, - essentially a scaled blit, and it is only useful for - applications which are already using (or can be modified to - use) XPutImage. Therefore, a more general API will be - discussed as another possibility. -

-

- X applications typically create windows with the - XCreateWindow call. A new extension could provide an - XCreateScaledWindow call that could be used in place of the - XCreateWindow call and be otherwise transparent to the - application. This would allow applications, even those that - do not depend on XPutImage, to take advantage of window - scaling. In this section we describe how the call would - work, what transparency it provides, and how to solve the - potential problems that transparency creates. -

- XCreateWindow -

- The XCreateWindow call takes width and height as - parameters. An XCreateScaledWindow call could take all - the same parameters, with the addition of a scaling factor. -

- - XSetWindowAttributes -

- An X11 window has several attributes that would have to be - scaled: - - Background and border pixmaps - Border width - Cursor - -

- - XGetWindowAttributes, XGetGeometry -

- For transparency, calls that query the window attributes - should return unscaled information. This suggests that - all unscaled pixmaps and window attributes should be - cached. -

-

- Unfortunately, a window manager requires the scaled - geometry to properly decorate the window. The X server - can probably determine which client is acting as the - window manager (e.g., because that client will select - events that are used exclusively by the window manager). - However, other Scaled Window Extension aware clients may - also need to determine the scaled geometry. Therefore, at - least two additional extension calls should be - implemented: XGetScaledWindowAttributes and - XGetScaledGeometry. -

- - Popup and Child window positions -

- Some applications may position popup and child windows - based on an unscaled notion of the main window geometry. - In this case, additional modifications to the client would - be required. -

- - Events -

- Most events (e.g., for mouse motion) return information - about the coordinates at which the even occurred. These - coordinates would have to be modified so that unscaled - values were presented to the client. -

- - Implementation -

- There are many implementation issues, some of which are - similar to the issues involved in implementing the X Video - Extension for DMX. The window contents must be scaled, - either by performing all operations to a frame buffer and - then writing the image to the display (perhaps using - hardware scaling support), or by modifying all of the - various drawing operations to perform scaling. Because of - the complexity involved, the frame buffer option is - recommended. -

- - - - - Conclusion and Recommendations -

- We recommend a three phase implementation strategy, based on - how an application could be written to take advantage of - scaling: - - -

- The XCopyAreaScaled extension should be implemented, since - this is the ideal solution for applications like VNC, and - since making use of this extension will require minimal - changes to applications that already use XPutImage or - XCopyArea. -

- The initial implementation work would include the design - of the X protocol extension, writing this up in the - usual format for extension documentation, implementation - of the protocol transport pieces in XFree86, - implementation of a software fall-back in XFree86 and - DMX, one example hardware implementation for XFree86, - and implementation of support for this extension in DMX. -

- We suggest implementing the extension first on the ATI - Radeon cards. However, since these cards do not provide - a 2D scaled blit primitive, the implementation would - have to make use of the 3D texture engine to emulate a - scaled blit. This is recommended, since other modern - graphics cards also do not provide a simple 2D scaled - blit operation and an example of the more difficult - implementation pathway would be helpful to others. - - -

- Until XCopyAreaScaled is widely supported, applications - that require scaling will have to fall back to another - scaling method. We suggest OpenGL as the first fall-back - method because it is widely available and supported by - DMX. -

- A project centered around OpenGL-based scaling would - implement this scaling in VNC as an example. This work - would include re-writing the vncviewer - rendering engine to cache a master copy of the desktop - image for all operations. - - -

- Since OpenGL is not implemented everywhere, and may not - provide hardware-assisted performance in every - implementation, an application that requires scaling - should also fall back to using the X Video Extension. -

- This project would add support for the X Video Extension - to DMX and would add support to VNC to take advantage of - this extension without introducing artifacts. This - would require modifying the vncviewer rendering - engine to cache a master copy of the desktop image for - all operations. This project should also add support - for the RGB format to at least one XFree86 driver (e.g., - ATI Radeon). -

- The X Video Extension is one of the few popular - extensions that DMX does not support. We recommend - implementing the X Video Extension even if scaling is - the specific goal of that work. - - -

-

- We do not recommend implementation of the - XCreateScaledWindow extension because of the complexity - involved. We do not recommend implementation of the - XPutImageScaled extension because it requires the same amount - of work as the XCopyAreaScaled extension, but provides less - functionality. Further, server-side scaling with a large - frame buffer is not recommended because of the - performance implications. -

-

- The back-end scaling, especially with disconnect/reconnect - support should be explored in the future after - disconnect/reconnect is implemented, but not at the present - time. -

- - -
- - - diff --git a/xorg-server/hw/dmx/doc/scaled.xml b/xorg-server/hw/dmx/doc/scaled.xml new file mode 100644 index 000000000..575cafd9d --- /dev/null +++ b/xorg-server/hw/dmx/doc/scaled.xml @@ -0,0 +1,725 @@ + + +
+ + + + Scaled Window Support in DMX + + Kevin E.Martin + Rickard E.Faith + + 15 October 2003 (created 19 September 2003) + + + This document investigates the possibility of adding scaled window + support to the DMX X server, thereby allowing a window or some + selected part of the logical DMX area to be displayed using a + scaling factor. For example, this might allow the contents of a + window to be magnified for easier viewing. In particular, scaling + for the VNC client is explored. Copyright 2003 + by Red Hat, Inc., Raleigh, North Carolina + + + + + + Introduction + DMX + + The DMX X server (Xdmx) is a proxy server that is designed + to allow X servers on multiple machines to be combined into + a single multi-headed X server. Combined with Xinerama, + these heads can appear as a single very high-resolution + screen. Typical applications include the creation of a + video wall with 16 1280x1024 displays arranged in a + rectangle, for a total resolution of of 5120x4096. + + + Problem Statement + + Applications displayed on a physically large video wall that + provides high pixel-resolution may be difficult to see, + especially if the application is designed for use on a + typical desktop computer with a relatively small display + located close to the human operator. The goal of this paper + is to describe and discuss solutions to this problem. + + + The original driving problem for this work is to provide + scaling for the vncviewer application when + displayed using DMX (VNC scaling is currently available only + with the Windows client, and there is no plan to extend that + capability to other clients). While this specific problem + will be addressed in this paper, the general solution space + will also be explored, since this may lead to a good + solution not only for vncviewer but also for + other applications. + + + Task + + For reference, here is the original description of the task + this paper addresses: + + Scaled window support (for VNC) + + + Investigate possibility of implementing a "scaled + window" extension: + + + Add XCreateScaledWindow call that could be used + in place of XCreateWindow + + + All primitives drawn to scaled window would be + scaled by appropriate (integral?) scaling factor + + + + + Alternate approach: special case VNC support + + + + + + + + + Previous Work + + This section reviews relevant previous work. + + VNC + Scaling under VNC + + When using the vncviewer program for Windows, it + is possible to specify a scaling factor (as numerator and + denominator). When scaling is in effect, the viewer + software uses StretchBlt (instead of BitBlt) to display + the pixels for the user. When this call is made, the + viewer already has received all of the pixel information + (at full unscaled resolution). + + + The scaling in VNC is primitive. It does not conserve + bandwidth, it does not treat textual information + differently (i.e., by using a suitably scaled font), and + it does not provide any anti-aliasing other than that + provided by the underlying (Windows-only) system library. + + + + The X Video Extension + + The X Video Extension is a widely-available extension to the + X11 protocol that provides support for streaming video. + Integral to this support is the ability to arbitrarily scale + the output. In version 2.2 of the X Video specification, + support for scaled still images was provided, using both + shared memory and traditional transport. The API for this + support uses calls that are quite similar to XCreateWindow, + XPutImage, and XShmPutImage. Currently, most of the drivers + implemented in XFree86 only support data in various YUV + formats. However, several modern video adaptors support RGB + as well. + + + Note, though, that the target output for this scaling is an + overlay plane -- so X Video provides functionality that is + fundamentally different from that provided by the Windows + StrechBlt call. + + + + + Possible Solutions + + This section briefly discusses possible solutions, including + major advantages and disadvantages from both the + implementation and the end-user programmer standpoint. + + VNC-like Scaling + Software Scaling + + The vncviewer application could be modified to + provide software scaling. This is not a general solution, + but it does solve one of the goals of this work. + + + A prototype of this solution was implemented and a patch + against vnc-3.3.7-unixsrc is available in the + dmx/external directory. Because of limited time + available for this work, all of the edge cases were not + considered and the solution works well mainly for integer + scaling. + + + Currently, vncviewer writes to the X display + with XPutImage, XCopyArea, and XFillRectangle. All + instances of these calls have to be aware of scaling + and must round correctly. In the prototype solution, + rounding is incorrect and can cause artifacts. + + + A better solution would be to cache all updates to the + desktop image in vncviewer and only send the + damaged area to the X display with XPutImage. This would + allow the damaged area to be computed so that rounding + errors do not create artifacts. This method is probably + similar to what is used in the Window client. (The whole + VNC suite is being re-written in C++ and the forthcoming + version 4 has not been evaluated.) + + + Scaling with the X Video Extension + + The scaling in the Windows vncviewer application + makes use of a scaled blit that is supplied by the + underlying system library. Several video cards currently + provide support for a scaled blit, and some X servers + (including XFree86) expose this capability to applications + via the XvPutImage interface of the X Video Extension. + The capability exposed by XvPutImage results in the scaled + image being drawn to an overlay plane. Most video cards + also provide support for a scaled blit into the normal + output planes, but this is not exposed via XvPutImage. + + + The vncviewer program could be modified to use + the X Video Extension to provide scaling under X11 that is + similar to the scaling currently provided under Windows. + Unfortunately, Xdmx does not currently export the X Video + Extension, so this would not provide an immediate solution + usable with DMX. + + + A very early-stage proof-of-concept prototype was + implemented and a preliminary patch against + vnc-3.3.7-unixsrc is available in the + dmx/external directory. This prototype was + implemented to better understand the problems that must be + solved to make this solution viable: + + + As noted under the software scaling section above, + vncviewer writes to the X display with + several different calls. These calls write to the + normal output planes and are compatible with + XvPutImage, which writes to an overlay plane. To + eliminate artifacts caused by this problem, + vncviewer should be modified so that a cached + copy of the desktop is available, either as a + client-side image or a server-side off-screen pixmap, + so that XvPutImage would be the only method for + writing to the X display. + + + + Although several modern graphics adaptors support + hardware scaling using an RGB format (e.g., ATI + Radeon, nVidia, etc.), XFree86 drivers typically + only implement YUV formats. YUV generally compress + the pixel information in some way. For example, two + commonly implemented formats, YUY2 and UYVY provide + intensity information for every RGB pixel, but only + provide chroma and luminance information for pairs + of horizontal pixels. Since VNC uses + pixel-resolution for communicating updates on the + wire, additional artifacts are introduced (because + there may not be enough information from the wire to + update a pair of pixels). + + + Further, the well-known problem with YUV encoding + is even more evident when the image is a desktop + instead of a movie. For example, consider a + 1-pixel-wide vertical window border. If the border + changes in color but not intensity (e.g., because a + window manager uses color to indicate focus), there + may or may not be a change in the YUY2 image, + depending on the algorithm used for RGB to YUV + conversion and on how the border pixel is ordered in + the pair of pixels used by the algorithm. + + + Many of these artifacts could be eliminated if + vncviewer cached a complete RGB image of + the desktop, and only did the conversion to YUV for + properly aligned areas of damage. The remaining artifacts + could be eliminated if an RGB format was used with X + Video (which may require the extension of existing + XFree86 drivers to support RGB). + + + + Most modern video cards support exactly one overlay + plane that is suitable for use with X Video. + Therefore, only one application can use X Video at any + given time. This is a severe limitation in a desktop + environment. + + + + Implementing the X Video Extension for DMX + + The user-level API for X Video is fairly simple, but the + underlying support required for the full specification + is large. However, since the API provides a method to + query supported capabilities, a usable subset of X + Video can be implemented that would support XvPutImage + and little else. This would require support for the + following: + + + X Video Extension API calls, including the + following: + + XvQueryExtension + XvQueryAdaptors + XvQueryPortAttributes + XvFreeAdaptorInfo + XvListImageFormats + XvGrabPort + XvCreateImage + XvPutImage + XvShmCreateImage + XvShmPutImage + + + + Support for querying back-end X Video Extension + capabilities. + + + Support for sending the image to the back-ends. + Because X Video requires sending full images, there + may be a trade-off between bandwidth limitations and + additional complexity to divide the image up such + that is scales properly. + + + Possible support for a software fall-back. For + example, if all of the back-ends do not support the X + Video Extension, software scaling can be implemented + such that the image is sent to the back-end with + XPutImage. This pathway would have poor + performance. + + + + + Supporting RGB formats for the X Video Extension + + Assuming an XFree86 driver already supports the X Video + Extension, and assuming the target hardware supports an + RGB format, then adding support for that format is + relatively simple and straightforward. + + + + Scaling with an XPutImageScaled Extension + + Instead of (or in addition to) implementing the X Video + Extension in DMX, one obvious solution would be to + implement a new extension that provides access to + hardware-assisted scaled blits, similar to the StretchBlt + call available under Windows. This call would scale RGB + images and would not use the overlay plane (unlike the X + Video Extension). + + + This approach has many of the same advantages and + disadvantages as the XCopyAreaScaled Extension, discussed + in the next section. Discussion of XPutImageScaled is + deferred in favor of XCopyAreaScaled for the following + reasons: + + + XPutImageScaled can be emulated with XCopyAreaScaled + by first using XPutImage to copy the image to an + off-screen pixmap, and then calling XCopyAreaScaled + between that off-screen pixmap and the target + drawable. + + + Since XCopyAreaScaled would copy between two areas of + on-screen or off-screen memory, it has additional uses + and can be viewed as efficiently providing a superset + of XPutImageScaled functionality. + + + + + Scaling with an XCopyAreaScaled Extension + + As noted in the previous section, because XCopyAreaScaled + provides a superset of the functionality provided by + XPutImageScaled, we will consider this extension instead. + + + First, XCopyAreaScaled would provide for RGB scaling + between pixmaps (i.e., on-screen or off-screen areas of + memory that reside on the video card). Unlike the X Video + Extension, which writes into an overlay plane, + XCopyAreaScaled would write into the non-overlay areas of + the screen. Key points to consider are as follows: + + + Because different planes are involved, the two scaling + operations are usually implemented in hardware + differently, so an XCopyAreaScaled extension could be + added in a manner that would neither conflict with nor + interact with the X Video extension in any way. + + + The XCopyAreaScaled extension provides new + functionality that the X Video Extension does not + provide. Based on anecdotal feedback, we believe that + many people outside the DMX and VNC communities would + be excited about this extension. + + + The main drawback to this extension is that it is new + and needs to be implemented at the driver level in + XFree86 for each video card to be supported. At the + present time, it is more likely that the X Video + Extension will be implemented for a particular piece + hardware because the X Video extension has multimedia + uses. However, over time, we would expect the + XCopyAreaScaled extension to be implemented along with + the X Video extension, especially if it becomes + popular. + + + Another drawback is that not all modern cards provide + support for a simple scaled blit operation. However, + these cards usually do provide a 3D pipeline which + could be used to provide this functionality in a + manner that is transparent to the client application + that is using the XCopyAreaScaled extension. However, + this implementation pathway would make this extension + somewhat more difficult to implement on certain cards. + + + + + Scaling with OpenGL + + Another general solution to the scaling problem is to use + the texture scaling found in all 3D hardware. This + ability is already exposed through OpenGL and can be + exploited by clients without X server modification (i.e., + other than the ability to support OpenGL). An application + using OpenGL would transmit the non-scaled image to the X + server as a texture, and would then display a single + non-transformed rect using that texture. This also works + around the single overlay problem with the X Video + Extension as well as the need to implement additional + scaled primitive extensions. + + + The downside is that most OpenGL implementations require + power of 2 texture sizes and this can be very wasteful of + memory if, for example, the application needs to scale a + 1025x1025 image, which would require a 2048x2048 texture + area (even a 640x480 image would require a 1024x512 + texture). Another downside is that some OpenGL + implementations have a limited about of texture memory and + cannot handle textures that are very large. For example, + they might limit the texture size to 1024x1024. + + + + Application-transparent Scaling for DMX + Back-end Scaling Without Disconnect/Reconnect + + VNC does scaling on the client side (in the + vncviewer application). Implementing a similar + solution for DMX would require support in the back-end X + servers and, therefore, is not a general solution. + + + XFree86 already implements some support for "scaling" that + could be used with DMX: if, in the XF86Config file, + multiple Modes are listed in the Display Subsection of the + Screen Section, then pressing Ctrl-Alt-Plus and + Ctrl-Alt-Minus can be used to iterate through the listed + modes. The display dimensions will change to the + dimensions in the Modes line, but the logical dimensions + of the X server (i.e., the dimensions that Xdmx knows + about) will not change. + + + Further, the dimensions of the XFree86 display are under + software control (via the XFree86-VidModeExtension), so + the Xdmx server could change the screen dimensions on a + per-display basis, thereby scaling the information on part + of that display. + + + However, this scaling appears to have limited use. For + example, assume a 4 by 4 display wall consisting of 16 + 1280x1024 displays. If all of the back-end servers were + simultaneously configured to display 640x480, the left + hand corner of each display would be magnified, but the + composite result would be unreadable. Magnifying one + display at a time could be usable, but could have limited + utility, since the result would still be no larger than a + single display. + + + Back-end Scaling With Disconnect/Reconnect + + Disconnect and reconnect features are not currently + supported in DMX, but are scheduled to be implemented in + the future. These features, combined with the + XFree86-VidModeExtension Extension, would allow an + application to do the following: + + + Disconnect a specific back-end server (via the DMX + Extension), + + + reconfigure the XFree86 back-end server resolution, + and + + + reconnect the back-end server to DMX -- at a new + origin with the new screen resolution. + + + + + For example, consider a display wall consisting of 16 + 1280x1024 displays with a total resolution of 5120x4096. + All of the screens could be disconnected, repositioned, + and reconnected each at a resolution of 640x480. The + total resolution of the display wall would be 2560x1920, + allowing a view of a selected area approximately + one-fourth of the size of the DMX display. This change + would be completely application independent (except, + perhaps, for a DMX-aware window manager). When work at + the increased resolution was completed, the back-end + servers could be disconnected, reconfigured, and + reconnected for the original 5120x4096 view. + + + Support for this type of scaling can be implemented in a + DMX-aware X11 client assuming the DMX server support + arbitrary disconnect and reconnect semantics. Because + this application cannot be written before + disconnect/reconnect is implemented, this solution will + not be discussed further in this paper. + + + Server-side Scaling + + In earlier versions of DMX, a frame buffer was maintained + on the server side, and XPutImage was used to move the + information from the server to the client (similar to some + early VNC implementations). The use of a server-side + frame buffer would allow the server to do scaling, but is + not a recommended solution because of overall performance + issues and server-side memory issues (i.e., the frame + buffer would be very large for large display walls). + + + Exploration of this path is not recommended. + + + + XCreateScaledWindow API + + The implementation of X Video Extension in DMX, and the use + of XvPutImage by applications requiring scaling requires + significant changes in DMX Further, XvPutImage is, + essentially a scaled blit, and it is only useful for + applications which are already using (or can be modified to + use) XPutImage. Therefore, a more general API will be + discussed as another possibility. + + + X applications typically create windows with the + XCreateWindow call. A new extension could provide an + XCreateScaledWindow call that could be used in place of the + XCreateWindow call and be otherwise transparent to the + application. This would allow applications, even those that + do not depend on XPutImage, to take advantage of window + scaling. In this section we describe how the call would + work, what transparency it provides, and how to solve the + potential problems that transparency creates. + + XCreateWindow + + The XCreateWindow call takes width and height as + parameters. An XCreateScaledWindow call could take all + the same parameters, with the addition of a scaling factor. + + + XSetWindowAttributes + + An X11 window has several attributes that would have to be + scaled: + + Background and border pixmaps + Border width + Cursor + + + + XGetWindowAttributes, XGetGeometry + + For transparency, calls that query the window attributes + should return unscaled information. This suggests that + all unscaled pixmaps and window attributes should be + cached. + + + Unfortunately, a window manager requires the scaled + geometry to properly decorate the window. The X server + can probably determine which client is acting as the + window manager (e.g., because that client will select + events that are used exclusively by the window manager). + However, other Scaled Window Extension aware clients may + also need to determine the scaled geometry. Therefore, at + least two additional extension calls should be + implemented: XGetScaledWindowAttributes and + XGetScaledGeometry. + + + Popup and Child window positions + + Some applications may position popup and child windows + based on an unscaled notion of the main window geometry. + In this case, additional modifications to the client would + be required. + + + Events + + Most events (e.g., for mouse motion) return information + about the coordinates at which the even occurred. These + coordinates would have to be modified so that unscaled + values were presented to the client. + + + Implementation + + There are many implementation issues, some of which are + similar to the issues involved in implementing the X Video + Extension for DMX. The window contents must be scaled, + either by performing all operations to a frame buffer and + then writing the image to the display (perhaps using + hardware scaling support), or by modifying all of the + various drawing operations to perform scaling. Because of + the complexity involved, the frame buffer option is + recommended. + + + + + + Conclusion and Recommendations + + We recommend a three phase implementation strategy, based on + how an application could be written to take advantage of + scaling: + + + + The XCopyAreaScaled extension should be implemented, since + this is the ideal solution for applications like VNC, and + since making use of this extension will require minimal + changes to applications that already use XPutImage or + XCopyArea. + + + The initial implementation work would include the design + of the X protocol extension, writing this up in the + usual format for extension documentation, implementation + of the protocol transport pieces in XFree86, + implementation of a software fall-back in XFree86 and + DMX, one example hardware implementation for XFree86, + and implementation of support for this extension in DMX. + + + We suggest implementing the extension first on the ATI + Radeon cards. However, since these cards do not provide + a 2D scaled blit primitive, the implementation would + have to make use of the 3D texture engine to emulate a + scaled blit. This is recommended, since other modern + graphics cards also do not provide a simple 2D scaled + blit operation and an example of the more difficult + implementation pathway would be helpful to others. + + + + + Until XCopyAreaScaled is widely supported, applications + that require scaling will have to fall back to another + scaling method. We suggest OpenGL as the first fall-back + method because it is widely available and supported by + DMX. + + + A project centered around OpenGL-based scaling would + implement this scaling in VNC as an example. This work + would include re-writing the vncviewer + rendering engine to cache a master copy of the desktop + image for all operations. + + + + + Since OpenGL is not implemented everywhere, and may not + provide hardware-assisted performance in every + implementation, an application that requires scaling + should also fall back to using the X Video Extension. + + + This project would add support for the X Video Extension + to DMX and would add support to VNC to take advantage of + this extension without introducing artifacts. This + would require modifying the vncviewer rendering + engine to cache a master copy of the desktop image for + all operations. This project should also add support + for the RGB format to at least one XFree86 driver (e.g., + ATI Radeon). + + + The X Video Extension is one of the few popular + extensions that DMX does not support. We recommend + implementing the X Video Extension even if scaling is + the specific goal of that work. + + + + + + We do not recommend implementation of the + XCreateScaledWindow extension because of the complexity + involved. We do not recommend implementation of the + XPutImageScaled extension because it requires the same amount + of work as the XCopyAreaScaled extension, but provides less + functionality. Further, server-side scaling with a large + frame buffer is not recommended because of the + performance implications. + + + The back-end scaling, especially with disconnect/reconnect + support should be explored in the future after + disconnect/reconnect is implemented, but not at the present + time. + + + +
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