linux-kernel - Re: [patch] CFS scheduler, -v19

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Date:	Wed, 11 Jul 2007 22:55:56 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Bill Davidsen <davidsen@....com>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Subject: Re: [patch] CFS scheduler, -v19


* Bill Davidsen <davidsen@....com> wrote:

> > I've taken mainline git tree (freshly integrated CFS!) out for a 
> > multimedia spin.  I tested watching movies and listenign to music in 
> > the presence of various sleep/burn loads, pure burn loads, and mixed 
> > loads. All was peachy here.. I saw no frame drops or sound skips or 
> > other artifacts under any load where the processor could possibly 
> > meet demand.
>
> I would agree with preliminary testing, save that if you get a lot of 
> processes updating the screen at once, there seems to be a notable 
> case of processes getting no CPU for 100-300ms, followed by a lot of 
> CPU.
> 
> I see this clearly with the "glitch1" test with four scrolling xterms 
> and glxgears, but also watching videos with little busy processes on 
> the screen. The only version where I never see this in test or with 
> real use is cfs-v13.

just as a test, does this go away if you:

	renice -20 pidof `Xorg`

i.e. is this connected to the way X is scheduled?

Another thing to check would be whether it goes away if you set the 
granularity to some really finegrained value:

    echo 0 > /proc/sys/kernel/sched_wakeup_granularity_ns
    echo 500000 > /proc/sys/kernel/sched_granularity_ns

this really pushes things - but it tests the theory whether this is 
related to granularity.

	Ingo
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