[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 #11 from Michel Dänzer <michel at daenzer.net> 2011-05-09 07:04:50 PDT ---
(In reply to comment #10)
> (In reply to comment #9)
> > Really sounds like the GPU IRQ doesn't work (reliably). Do the numbers on the
> > radeon line in /proc/interrupts still increase when the problem occurs?
> 
> Not a lot.  When everything's working, moving wobbly windows involves hundreds
> of interrupts.  When it's at 2 fps, there are only a few, at most.  Possibly
> none.

That probably explains the slowness, as the drivers heavily rely on the IRQ for
tracking GPU progress processing commands. With no interrupts coming in, things
will time out all over the place.

The question now is why there are no interrupts coming in...

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