linux-kernel - Re: Sched_autogroup and niced processes

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Message-ID: <20110513090537.GH13647@elte.hu>
Date:	Fri, 13 May 2011 11:05:37 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Mike Galbraith <efault@....de>, Yong Zhang <yong.zhang0@...il.com>,
	Carl-Johan Kjellander <carl-johan@...rna.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Sched_autogroup and niced processes

* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Fri, 2011-05-13 at 10:22 +0200, Ingo Molnar wrote:
> > * Mike Galbraith <efault@....de> wrote:
> > 
> > > > > 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
> > 
> > I think the practical question here is to make seti@...e run more idle.
> > 
> > Are there some magic cgroup commands you could recommend for that?
> 
> Yong already did.

Oh, indeed, stupid me. This teaches me to not stop at the first paragraph of 
interesting looking emails ;-)

Could we somehow automate this:

  > echo 19 > /proc/'pid of seti@...e'/autogroup

and split off nice 19 tasks into separate groups and lower the group's 
priority?

That would fit into the general principle of auto-sched as well.

Another thing we could do is to lower the priority of a cgroup if it *only* 
runs reniced tasks. I.e. track the 'maximum priority' of cgroups and propagate 
that to their weight.

This way renicing within cgroups will be more powerful and people do not have 
to muck with cgroup details.

Thanks,

	Ingo
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