Date: Sun, 30 Sep 2007 19:27:36 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Matthew <jackdachef@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [patch/backport] CFS scheduler, -v22, for v2.6.23-rc8,
	v2.6.22.8, v2.6.21.7, v2.6.20.20
Message-ID: <20070930172736.GA12299@elte.hu>
References: <e85b9d30709290411u4f48d716o3260bab7d71261ff@mail.gmail.com> <20070930154354.GD24077@elte.hu> <e85b9d30709300943rded9801xddc6ca0a4773ff53@mail.gmail.com>
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* Matthew <jackdachef@gmail.com> wrote:

> Thanks for your answer (sorry, I didn't know your email had changed)
> 
> well, this will take some time since I don't work every day & it's 
> turned off most of the time, hope that is OK
> 
> before I proceed with that data-collection:
> 
> do you think it is possible that it might be related to "Fair group 
> CPU scheduler" being selected ?

i think if you are relatively sure that the box does not have any real 
3D hardware in it (supported by X) then glxgears will interact badly 
with X and can cause such symptoms. In that case glxgears 'spams' the X 
server with requests and everyone else suffers from that. The fair-group 
scheduler indeed could shift CPU usage of X just enough (in X's favor!) 
that might trigger such problems. Such "spam X" workloads often react in 
a paradoxial way: a scheduler that gives X _more_ CPU time will appear 
to be "less interactive".)

	Ingo
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