linux-kernel - Re: CFS review

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Date:	Wed, 29 Aug 2007 11:53:30 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Ingo Molnar <mingo@...e.hu>,
	Keith Packard <keith.packard@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: CFS review

Ingo Molnar wrote:
> * Keith Packard <keith.packard@...el.com> wrote:
> > Make sure the X server isn't running with the smart scheduler
> > disabled; that will cause precisely the symptoms you're seeing here.
> > In the normal usptream sources, you'd have to use '-dumbSched' as an X
> > server command line option.
> >
> > The old 'scheduler' would run an entire X client's input buffer dry
> > before looking for requests from another client. Because glxgears
> > requests are small but time consuming, this can cause very long delays
> > between client switching.
>
> on the old box where i've reproduced this i've got an ancient X version:
>
>   neptune:~> X -version
>
>   X Window System Version 6.8.2
>   Release Date: 9 February 2005
>   X Protocol Version 11, Revision 0, Release 6.8.2
>   Build Operating System: Linux 2.6.9-22.ELsmp i686 [ELF]
>
> is that old enough to not have the smart X scheduler?
>
> on newer systems i dont see correctly updated glxgears output (probably
> the GLX bug you mentioned) so i cannot reproduce the bug.
>
> Al, could you send us your 'X -version' output?

This is the one I have been talking about:

XFree86 Version 4.3.0
Release Date: 27 February 2003
X Protocol Version 11, Revision 0, Release 6.6
Build Operating System: Linux 2.4.21-0.13mdksmp i686 [ELF] 


I also tried the gears test just now on this:

X Window System Version 6.8.1
Release Date: 17 September 2004
X Protocol Version 11, Revision 0, Release 6.8.1
Build Operating System: Linux 2.6.9-1.860_ELsmp i686 [ELF] 

but it completely locks up.  Disabling add_wait_runtime seems to fix it.


Thanks!

--
Al

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