linux-kernel - Re: [patch] Re: scheduler oddity [bug?]

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Message-Id: <1236607083.5980.8.camel@marge.simson.net>
Date:	Mon, 09 Mar 2009 14:58:03 +0100
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, Balazs Scheidler <bazsi@...abit.hu>,
	linux-kernel@...r.kernel.org, Willy Tarreau <w@....eu>
Subject: Re: [patch] Re: scheduler oddity [bug?]

On Mon, 2009-03-09 at 14:46 +0100, Peter Zijlstra wrote:
> On Mon, 2009-03-09 at 14:37 +0100, Mike Galbraith wrote:
> > On Mon, 2009-03-09 at 14:16 +0100, Mike Galbraith wrote:
> > > On Mon, 2009-03-09 at 12:04 +0100, Peter Zijlstra wrote:
> > > 
> > > > OK, talked a bit with Ingo, the reason you're doing is that avg_overlap
> > > > can easily grow stale.. I can see that happen indeed.
> > > > 
> > > > So the 'perfect' thing would be a task-runtime decay, barring that the
> > > > preemption thing seems a sane enough hart-beat of a task.
> > > > 
> > > > How does the below look to you?
> > > 
> > > Other than the fact that the test for sync reject is currently
> > > avg_overlap > sysctl_sched_migration_cost, looks fine to me.  Having it
> > > capped at the boundary is probably the better way to go.
> > 
> > Heh, doesn't _quite_ work though.  The little bugger now hovers just
> > under :-/
> 
> > se.avg_overlap                     :             0.499993
> 
> Right, update_avg()'s >>3 and the off-by-one you spotted.

(that was with the off-by-one fixed, but..)

> I recon stuff works better with a 2* added? After that I guess its
> praying sysbench still works.. :-)

Yes 2* worked fine.  Mysql+oltp was my worry spot, being a very affinity
sensitive little <bleep>, but my patchlet didn't cause any trouble, so
this one shouldn't either.  I'll do some re-test in any case, and squeak
should anything turn up.

	-Mike

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