radeon EXA performance questions

Simon Thum simon.thum at gmx.de
Mon Aug 4 12:40:01 PDT 2008

Owen Taylor wrote:
> That CPU time is spent here doesn't necessarily mean that this the
> actual bottleneck... GetImage needs to wait for the GPU to become
> idle, and that involves a busy-wait currently. (At least with the DRM,
> and probably otherwise.)
That makes sense given the XAA code doesn't make much use of locks.

> When I've seen GetImage taking most of the CPU, that's typically meant
> that drawing in general is GPU bound, so the CPU gets ahead of the
> GPU and blocks in GetImage. 
Just out of curiosity: Is the FB (b)locked as whole?

> I can't find the actual profile in the list archives, so I'm not sure if
It was a bit too big.
> the CPU time is waiting for the GPU to go idle, or it's actually
> spent in the copying itself, which would indicate a different sort of
> problem ... perhaps cairo is using extensive software fallbacks for some
> reason.
I used Thunderbird 1.5/FF2, which AFAIK rules out cairo. Michel 
suggested the missing DRI to be the problem. If there is interest in the 
profile or a profile of special cases can do them.



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