9.1 Proposal: Top five performance problems

[Jordan Crouse]

On 25/10/08 00:00 +0200, NoiseEHC wrote:
> The Geode X drive copyes every bit of data to the command ring buffer by 
> using the CPU so that is sure that those "almost no CPU cycles" thing is 
> at least a bit stretch... :) According to Jordan Crouse it will not be 
> better but he was not too concrete so in the end I am not sure what he 
> was really talking about, see:
> http://lists.laptop.org/pipermail/devel/2008-May/014797.html

Indeed - many CPU cycles are used during compositing.  There is a lot of
math that happens to generate the masks and other collateral to render
the alpha icon on the screen.  The performance savings in the composite
code comes from not having to read video memory to get the src pixel
for the alpha operation(s).  That performance savings is already available
in the X driver today.

Jordan

> Benjamin M. Schwartz wrote:
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> > Erik Garrison wrote:
> >   
> >> What about changing the kind of visual feedback we give.  Instead of
> >> pulsing icons what about icons with a string of dots beneath, a progress
> >> bar, flashing, or another kind of overlay feedback which requires fewer
> >> visual changes (frames) and/or could be overlaid on top of existing
> >> icons without calculating a new animation for every icon?
> >>     
> >
> > We have GPU-accelerated alpha compositing on the XO, so we could do the
> > current animation using almost no CPU cycles.  It's just a question of
> > figuring out how to access that compositing.  As far as I'm aware, no
> > effort in this direction has been made.  I don't know if "composite" here
> > requires the use of "Composite" in the window manager or not; my knowledge
> > of X is minimal.
> >
> > - --Ben
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-- 
Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.