linux-kernel - Re: [patch] CFS scheduler, -v18

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Date:	Tue, 3 Jul 2007 09:15:12 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [patch] CFS scheduler, -v18

* Vegard Nossum <vegard.nossum@...il.com> wrote:

> I'd also like to point out that Folding@...e seems to draw more CPU 
> than it should. Or, at least, in top, it shows up as using 50% CPU 
> even though other processes are demanding as much as they can get. The 
> FAH program should be running with idle priority. I expect it to fall 
> to near 0% when other programs are running at full speed, but it keeps 
> trotting along. And I am pretty sure that this is not due to SMP/HT (I 
> made sure to utilize both CPUs).

your FAH processes are running with nice +19 - that should be enough to 
throttle them. With v18 you can also mark it SCHED_IDLE:

    schedtool -D $$  # mark the shell idle

SCHED_IDLE gets inherited by child tasks so if you mark the shell that 
starts up FEH as SCHED_IDLE, all FEH threads should be SCHED_IDLE too. 
(or you can start it up via schedtool -D -e ... )

does it still get more CPU time than you'd expect it to get? A reniced 
or SCHED_IDLE task will 'fill in' any idle time that it senses, so in 
itself it's not an anomaly if a task gets 50% and FEH fills in the 
remaining 50%. Does it still get CPU time if you start two CPU hogs:

   for (( N=0; N < 2; N++ )); do ( while :; do :; done ) & done

? If yes, that would be an anomaly.

> Otherwise, I am satisfied with the performance of CFS. Especially the 
> desktop is noticably smoother. Thanks!

great! :-)

	Ingo
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