Comment 29 for bug 578342

I've noticed that the audio glitches become a lot worse when many windows are open and running Compiz (I did an artificial test). I can open lots of windows on one desktop, switch back to an empty desktop, open a single window there and trigger audio drop-outs (simple test sound) just by toggling maximization state of that single window, even though all the other windows are not in view and system load is close to nil. Basically, most Compiz-operations besides simple window movement will cause glitches.

Interestingly, I might have pushed things too far, since Compiz crashed with this message:
drmRadeonCmdBuffer: -12. Kernel failed to parse or rejected command stream. See dmesg for more info.

Kernel log contained this:
[ 543.577306] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!
[ 574.532539] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!
[ 742.437808] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!

* This was all with radeon.disp_priority=1, cannot say whether that mattered or not.
* Don't know the consequences of using the Ubuntu default Xorg-driver/libdrm/DRI-stuff together with 2.6.34 mainline kernel DRM. I haven't noticed any bad things in particular during normal usage (quite the contrary, KMS performance with 2.6.34 seems better), except for the issues at hand of course.
* The version of the radeon module in the default Ubuntu kernel does not have disp_priority option.