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List:       kwin
Subject:    Re: __GL_YIELD
From:       Lubos Lunak <l.lunak () suse ! cz>
Date:       2007-05-14 16:09:52
Message-ID: 200705141809.52993.l.lunak () suse ! cz
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On Sunday 13 of May 2007, Ignacio Castano wrote:
> Lubos,
>
> I had a conversation the other day with the Linux driver team about
> __GL_YIELD, and we think it's not a good idea to set it to NOTHING by
> default. That's just a temporary workaround for the lack of a snappy
> sched_yield() function on linux. We have discussed our discontent
> with the kernel development community and we hope this is something
> will be fixed in the future.

 It hasn't been decided yet but it probably won't be the default. The point is 
only about providing an easy way to enable it, since setting the env.variable 
only for KWin is not trivial due to the way KWin is launched during KDE 
startup and AFAIK it needs to be set even before main() is reached, so KWin 
cannot trivially set it for itself either.

> What we are going to do now is to add kwin to our performance tests
> to make sure it performs as well as possible in future drivers. If we
> find that yield causes significant slowdowns, we will implement
> workarounds, and if they require changes on your side, we will send
> you patches and suggestions.
>
> BTW, if you have questions or comments about our drivers or our
> hardware, feel free to send them to me, and I'll forward them to the
> right person.

 A list of driver/card-specific issues can be found in 
http://websvn.kde.org/*checkout*/trunk/KDE/kdebase/workspace/kwin/COMPOSITE_HOWTO 
(and COMPOSITE_TODO). Actually personally what currently bothers me the most 
is that there are sometimes lockups when launching second X session (I use an 
extra one for development) and that two of my three gfx cards are already 
considered legacy (which I suppose are not worth bothering for nvidia), but 
otherwise I'm generally rather satisfied with using nvidia cards.

-- 
Lubos Lunak
KDE developer
--------------------------------------------------------------
SUSE LINUX, s.r.o.   e-mail: l.lunak@suse.cz , l.lunak@kde.org
Lihovarska 1060/12   tel: +420 284 028 972
190 00 Prague 9      fax: +420 284 028 951
Czech Republic       http//www.suse.cz
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