[Bug 21683] EXA on radeon chip seems to trigger serious performance issues

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Jun 2 09:28:48 PDT 2009


--- Comment #21 from Roland Scheidegger <sroland at tungstengraphics.com>  2009-06-02 09:28:48 PST ---
(In reply to comment #20)
> (In reply to comment #13)
> > Created an attachment (id=25890)
 --> (http://bugs.freedesktop.org/attachment.cgi?id=25890) [details] [details]
> > use XAA in low memory situations or when the DRI is disabled
> I don't think 32MB is too little. At least I think the ideal solution would be
> to set FBTexPercent to 0 with let's say less than 64MB. I set it with my
> Mobility 9000 (32MB) and EXA seems pretty fast for me (opposed to what is was
> before setting FBTexPercent).
> So if you know how to check it / do it, I'd propose FBTexPercent 0 for <65535
> and XAA for <32768 (not <=).
This hurts 3d performance pretty bad though afair. We should actually do the
opposite, make ddx only use gart (I don't think it really would make much
difference to 2d performance), though I don't think this can easily be done. Or
just use some same memory management.

> I additionally tested setting DepthBits to 16 which halves the memory usage for
> that buffer, but didn't notice any specific improvement in this case besides
> Xorg.0.log stating more memory could be used for EXA. It does generate issues
> in some 3D stuff but eg. compiz works fine.
I don't think compiz uses depth buffer at all and even if it does it would
probably be fine with very few depth buffer bits.
Again, the real solution is in better memory management.

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