[PATCH] Ensure blitter quiescience before reading pixels from the framebuffer

[Carl Worth]

On Mon, 30 Jul 2007 16:39:44 +0200, Bernardo Innocenti wrote:
> Michel Dänzer wrote:
> > Adam Jackson fixed that in GIT.
> 
> This patch?
> 
>  http://gitweb.freedesktop.org/?p=xorg/xserver.git;a=commitdiff;h=486fd4145aed93093d1f1655de40c0a8582bb8b1
...
> > If there's still a measurable penalty in some cases with the above change,
> > this is probably the way to go.
> 
> I always wanted to run oprofile on one of Cairo's benchmark to see how the
> overhead is distributed.  But Carl Worth already provided plenty of proof.

How's that?

None of the benchmarks I've reported were after that commit.

> The overhead is quite visible also with the naked eye: after walking through the
> server-side code for drawing one trapezoid, I'm actually surprised it still runs
> so fast :-)

CPUs are pretty impressive that way. Single-stepping through the code
is definitely not the way to find bottlenecks. It all seems horribly
slow when you single step through piles of code, (but that doesn't
necessarily mean that those piles are the things that are causing
slowdowns).

-Carl
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