linux-kernel - Re: Sched_autogroup and niced processes

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Date:	Fri, 13 May 2011 15:53:04 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Carl-Johan Kjellander <carl-johan@...rna.com>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...e.hu>
Subject: Re: Sched_autogroup and niced processes

Cc'ing more people.

On Fri, May 13, 2011 at 3:39 PM, Carl-Johan Kjellander
<carl-johan@...rna.com> wrote:
> I've been running seti@...e niced to 19 in the background since 1999
> without any problems. No noticeable effect even when playing a movie
> or a game. But since 2.6.38 the new fix-all-problems automatic
> grouping has been messing a bit with me. These are some timed compiles
> on my 8 cores.
>
> time make -j12 # with seti@...e running
> real    4m16.753s
> user    10m33.770s
> sys     1m39.710s
>
> time make -j12 # without seti@...e running
> real    2m12.480s
> user    10m11.580s
> sys     1m39.980s
>
> echo 0 > /proc/sys/kernel/sched_autogroup_enabled
> time make -j12 # no autogroup, seti@...e running again
> real    2m33.276s
> user    10m37.540s
> sys     1m43.190s
>
> All compiles already had all files cached in RAM.
>
> Now I can take the 10% performance hit, but not the 100% hit of
> running stuff super niced in the background. Processes niced to 19
> should only use spare cycles and not take up half of the cores even
> with autogroup. I would really like to run autogroup since it is a
> neat idea, but it can't mess up running niced processes in the
> background which have been working fine for 12 years.

Then how about change the nice value of seti@...e->autogroup?
echo 19 > /proc/'pid of seti@...e'/autogroup

Thanks,
Yong

>
> /Carl-Johan Kjellander
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