linux-kernel - Re: [PATCH 1/2] Customize sched domain via cpuset

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Message-ID: <20080401132924.GI29105@one.firstfloor.org>
Date:	Tue, 1 Apr 2008 15:29:25 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Paul Jackson <pj@....com>
Subject: Re: [PATCH 1/2] Customize sched domain via cpuset

On Tue, Apr 01, 2008 at 01:56:08PM +0200, Peter Zijlstra wrote:
> On Tue, 2008-04-01 at 13:40 +0200, Andi Kleen wrote:
> > Hidetoshi Seto <seto.hidetoshi@...fujitsu.com> writes:
> > 
> > > Using cpuset, now we can partition the system into multiple sched domains.
> > > Then, how about providing different characteristics for each domains?
> > 
> > Did you actually see much improvement in any relevant workload
> > from tweaking these parameters?  If yes what did you change?
> > And how much did it gain?
> > 
> > Ideally the kernel should perform well without much tweaking
> > out of the box, simply because most users won't tweak. Adding a 
> > lot of such parameters would imply giving up on good defaults which 
> > is not a good thing.
> 
> >From what I understand they need very aggressive idle balancing; much
> more so than what is normally healty.
> 
> I can see how something like that can be useful when you have a lot of
> very short running tasks. These could pile up on a few cpus and leave
> others idle.

Could the scheduler auto tune itself to this situation?

e.g. when it sees a row of very high run queue inbalances increase the
frequency of the idle balancer?

-Andi
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