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[Bug 361060] Re: [X1400] Extra X sessions very slow because of EXA and no DRI


** Changed in: xserver-xorg-video-ati (Ubuntu Karmic)
       Status: Confirmed => Won't Fix

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  [X1400] Extra X sessions very slow because of EXA and no DRI

Status in “xserver-xorg-video-ati” package in Ubuntu:
  Fix Released
Status in “xserver-xorg-video-ati” source package in Karmic:
  Won't Fix

Bug description:
  In Jaunty, EXA is enabled by default in the radeon driver. This works
  fine for the main login session (DISPLAY :0), provided that DRI is
  successfully initialized. However, DRI seems to only be available to
  the first X display instance, as the radeon driver fails to initialize
  DRI for extra sessions, like an additional "Guest session". This in
  combination with EXA being the default acceleration method makes for a
  very poor experience with extremely slow rendering for such sessions.
  I think EXA requires DRI to be able to perform OK (it certainly sucks
  without it on my machine). By using XAA acceleration for extra
  sessions that do not have DRI, the performance becomes acceptable.

  I don't know if Intel or Nvidia handle multiple X sessions and 3D
  acceleration/DRI, but it does not seem like the radeon driver does. I
  solved this by making sure any extra sessions use XAA instead of EXA.

  This is a quick hack I did, so extra sessions use XAA:
  1) Added the following to /etc/gdm/gdm.conf-custom:
  name=Standard server
  command=/etc/gdm/Xwrapper -br -audit 0

  2) Xwrapper is a simple script which checks if DISLPLAY is ':0' or not. If display is not ':0', then X is started
  with a configuration file that sets the radeon driver to use XAA acceleration:
  if [ "$1" != :0 ]; then
    exec /usr/X11R6/bin/X "$@" -config /etc/X11/xorg-extra.conf

  exec /usr/X11R6/bin/X "$@"

  3) /etc/X11/xorg-extra.conf is simply an Xorg config file that sets
  radeon driver to use XAA.

  The problem is that extra sessions in combination with the radeon
  driver become unusably slow because of the lack of DRI, so it should
  be solved in some way. Maybe the radeon-driver should select XAA
  instead of EXA when DRI fails to initialize ? Or is it perhaps
  possible to get EXA to perform OK without DRI ? I guess this won't be
  a problem when all the new DRI2/GEM/KMS stuff comes into place, but it
  certainly is a problem for current Ubuntu Jaunty.

  I have an ATI X1400 graphics card, and using of course radeon driver.
  Tracking Jaunty beta. I set the package hint in this bug to xserver-
  xorg-video-radeon, but I'm not sure that's appropriate.

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