First of all, sudo aptitude install mesa-utils. Then run in a Terminal/Konsole glxgears, and wait for ~15 seconds; if your FPS is ~400 or less, then you do have sluggish video performance (usually manifesting itself as slow scrolling in Firefox/Iceweasel, slow window switching/minimziing/maximizing etc).

After reading through several forums and bug reports and blog posts, I’ve ended with the following modifications to my /etc/X11/xorg.conf:

1. backup your current xorg.conf: sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.before-exa
2. open your /etc/X11/xorg.conf with a favourite editor; I’ve added these lines to section “module”:
   

   Load “dbe”
   Load “xtrap”
   Load “record”
   Load “GLcore”

   These are not really performance-related and could be skipped; I’m giving them here, because they were suggested as default entries by dexconf or some other xorg.conf-generator utility. Again – they are not supposed to improve performance, so you can skip these.

3. my “Device” section is now:
   

   Section “Device”
   Identifier “Intel Corporation 82915G/GV/910GL Integrated Graphics Controller”
   BoardName “82915G/GV/910GL Integrated Graphics Controller”
   Vendorname “Intel Corporation”
   #Driver “i810″
   Driver “intel”
   BusID “PCI:0:2:0″
   Option “DRI” “true”
   Option “AccelMethod” “exa”
   Option “MigrationHeuristic” “greedy”
   Option “ExaNoComposite” “false”
   EndSection

   Driver i810 (xserver-xorg-video-i810 package) was about 10-20 FPS slower than Driver intel (xserver-xorg-video-intel package) for me. The most important lines here are Option AccelMethod exa (which enables EXA acceleration instead of the older XAA; if you run 2.6.28 or later kernel, you can try UXA instead of EXA) and Option MigrationHeuristic greedy. Option ExaNoComposite false doesn’t make a difference for me, and Option DRI true might be redundant (didn’t bother trying to remove it).

4. at the end of xorg.conf I have two more sections:
   

   Section “DRI”
   Mode 0666
   EndSection

   Section “Extensions”
   Option “Composite” “enable”
   Option “MIT-SHM” “Yes”
   EndSection

5. sudo nano /etc/environment, and add one line: INTEL_BATCH=1 (if you have graphics stability issues or screen corruption – try removing this change first)
6. you can test if your xorg.conf is syntactically correct by running X -config /etc/X11/xorg.conf (provided that you edited this exact file)

This is it. Before these modifications, my FPS in glxgears was around 430; after these modifications it is ~915.

As time permits, I might try the XAA configuration, suggested at foolcontrol.

Update: with compiz enabled, XAA configuration recommended at foolcontrol is definitely faster in 2D.

Improvements, suggestions, corrections are welcome.

The Crisis of Credit Visualized by Jonathan Jarvis.