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Date: Tue, 1 Apr 2008 15:29:25 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>,
       Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
       Paul Jackson <pj@sgi.com>
Subject: Re: [PATCH 1/2] Customize sched domain via cpuset
Message-ID: <20080401132924.GI29105@one.firstfloor.org>
References: <47F21BE3.5030705@jp.fujitsu.com> <87zlsdzttp.fsf@basil.nowhere.org> <1207050968.8514.721.camel@twins>
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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@jp.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