[Bug 36596] Major 2D performance bottleneck (most noticeable with compiz)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=36596

--- Comment #6 from Michel Dänzer <michel at daenzer.net> 2011-04-29 02:06:53 PDT ---
(In reply to comment #4)
> The slowness coincides with very low CPU usage.

If sync to vblank is enabled in the compiz configuration, does disabling that
help? If not, does

 Option "EnablePageFlip" "off"

and/or

 Option "SwapbuffersWait" "off"

in xorg.conf help? (Verify in Xorg.0.log that the options are taking effect)


> Would it be useful to profile something anyway?

sysprof or oprofile won't be useful. If none of the above helps, it might be
possible to find out where compiz is blocking with something like perf, but I
don't know how offhand.


> BTW, I should have mentioned that I have to boot with the "noirqdebug" kernel
> parameter, otherwise the kernel will sometimes disable the Radeon's IRQ saying
> "irq 19: nobody cared" (the exact message is no longer in the logs).  Once the
> IRQ was disabled, everything still worked, but more slowly.

Hmm, the radeon IRQ not working reliably might explain at least some of your
symptoms. FWIW, can you also attach the dmesg output, at least the lines
related to agp/drm/radeon?

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