F16 slowness

[Adam Jackson]

On Thu, 2011-09-08 at 09:29 +0200, Matthias Runge wrote:
> On 07/09/11 21:06, Adam Williamson wrote:
> >> Is there a graphics benchmark to try out?
> > 
> > I don't see that a benchmark is going to tell you anything you
> > don't already know ('it's performing slow'). I'd suggest grabbing a
> > set of older kernel builds and booting them all to see if you can
> > find one which runs at normal speed and hence identify when the
> > breakage occurred.
> Sometimes, it's just a feeling. If we know numbers, we can show, this
> issue is fixed.
> 
> Yesterday there was an Xorg-Update (Xorg-common, Xorg-server). I'm
> nearly sure, this regression was fixed with that update, which circles
> me back to the benchmark-question.

I'm nearly sure it wasn't.

There have been two xserver updates between the 2011-05-11 snapshot and
now.  In a quick review of the changes in that interval I can only find
one change that looks even remotely like a performance improvement:

http://cgit.freedesktop.org/xorg/xserver/commit/?id=9504caf1c3243e3ab2eb7126bc2bb876a8f89918

And even that is pretty borderline.  It inhibits the normal implicit
draw that the server would do on exposure processing when a window has a
particular redirection mode set by the compositor, but a) when
composited, exposures are extremely rare, essentially only happening
when a window transitions from unmapped to mapped; and b) background
paints are _cheap_, usually just a solid fill of the grey from your
theme color, but even in the worst case just a tiled pixmap blit.

If all you're looking for is a "is config A faster than config B" kind
of measurement, then something like

% x11perf -copypixwin{10,100,500}

isn't completely misleading, although it's not uncommon for successive
x11perf runs to vary by up to 5%, and when composited the x11perf
benchmarks require _very_ careful understanding of just what exactly
you're measuring and can be wildly variable even within a single run.

I realize I'm begging to get inundated with x11perf scores by even
mentioning it.  Oh well.

- ajax
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