[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 09:38:10 PDT 2009


--- Comment #22 from Michel Dänzer <michel at daenzer.net>  2009-06-02 09:38:10 PST ---
(In reply to comment #20)
> At least I think the ideal solution would be to set FBTexPercent to 0 with
> let's say less than 64MB.

Unfortunately, the Mesa r300 driver traditionally doesn't support this, as it
uses the GART memory for vertex data. Though I'm not sure there are any
(discrete) cards this would affect, so it might still be feasible.

> 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 noticed recently that this option can't really work properly, as the 3D
driver doesn't get any information about the depth buffer size being different
from the colour depth. The option probably needs to be removed again.

Anyway, as Roland pointed out, these are really just hacks to fill the gap
until there is proper kernel graphics memory management.

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