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List:       kwin
Subject:    Re: __GL_YIELD
From:       jos poortvliet <jos () mijnkamer ! nl>
Date:       2007-05-02 12:44:04
Message-ID: 200705021444.08269.jos () mijnkamer ! nl
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Op Wednesday 02 May 2007, schreef Rivo Laks:
> Ühel kenal päeval (esmaspäev 30 aprill 2007) kirjutas Lubos Lunak:
> >  Hello,
> >
> >  does somebody know about details about %subj%? This
> > http://lists.freedesktop.org/archives/compiz/2007-April/001965.html
> > thread discusses some internal NVidia shell variable that should improve
> > performance.
>
> Hi
>
> From what I could find in the net, it tells the driver not to "yield it's
> timeslice" which seems to mean that driver won't donate it's own execution
> time to other programs. This would result in better performance, especially
> under heavy cpu load.

It sounds like an issue with interactivity, though. As you mention below, the 
animation goes smoother, but the window doesn't draw anymore. I guess what 
this does is ensure the GL part of the app gets all the CPU it can get it's 
hands on. If the window isn't doing anything else (or you can prevent the 
need for repaint by keeping the texture around), this would improve things 
visually. And if the GL code takes away from the 'work' the app has to do, I 
don't think that's a bad thing either - as long as you're not dealing with 
things like music and video playback. I can imagine those would get hurt.

I don't know much about the details here, but playing with the scheduler is a 
dangerous thing. So be a bit carefull, you'd want sound to continue playing 
if one does a desktop switch :D

> Experimenting shows that setting  __GL_YIELD="NOTHING"  really does improve
> (visible) performance. Especially animations feel a lot snappier with it,
> possibly because window repaints are more delayed towards the end of
> animation. So while the animation (e.g. desktop switch) is in progress, you
> mostly see just a white/grey window background and usually the window
> repaint is completed only at the end of the animation.
> BTW, can't we just keep the window texture around (window mapped or
> whatever the correct term is) instead of repainting it every time it's
> shown (e.g. on desktop switch)?
>
> So IMHO it would probably be a good idea to use __GL_YIELD when doing GL
> compositing.
>
> Rivo
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> Kwin@kde.org
> https://mail.kde.org/mailman/listinfo/kwin



-- 
Disclaimer:

Alles wat ik doe denk en zeg is gebaseerd op het wereldbeeld wat ik nu heb. 
Ik ben niet verantwoordelijk voor wijzigingen van de wereld, of het beeld wat 
ik daarvan heb, noch voor de daaruit voortvloeiende gedragingen van mezelf. 
Alles wat ik zeg is aardig bedoeld, tenzij expliciet vermeld.

Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html

   A: Because it destroys the flow of the conversation
   Q: Why is top-posting bad?

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