linux-kernel - Re: sched regression introduced by NO_NEW_FAIR

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Message-ID: <20091003144957.GA27943@elte.hu>
Date:	Sat, 3 Oct 2009 16:49:57 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	drago01 <drago01@...il.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>,
	kernel list <linux-kernel@...r.kernel.org>, mingo@...hat.com,
	Chuck Ebbert <cebbert@...hat.com>
Subject: Re: sched regression introduced by NO_NEW_FAIR_SLEEPERS


* drago01 <drago01@...il.com> wrote:

> On Sat, Oct 3, 2009 at 12:47 PM, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > * drago01 <drago01@...il.com> wrote:
> >
> >> On Sun, Sep 27, 2009 at 9:47 PM, drago01 <drago01@...il.com> wrote:
> >> > Hi,
> >> >
> >> > Chuck has backported some scheduler patches from 2.6.32 to the fedora kernel.
> >> >
> >> > I did the following test to test the new scheduler (cpu is a core i7
> >> > 920 4 cores + HT).
> >> >
> >> > run 8 "md5sum /dev/urandom" task and try to use the desktop (compiz).
> >> >
> >> > The result was that moving windows or rotating the cube is very slow.
> >> > (same happens with pure metacity but is is worse in compiz).
> >> >
> >> > Mounting debugfs and doing "echo NEW_FAIR_SLEEPERS > sched_features"
> >> > results into a useable desktop while the 8 md5sum tasks are running
> >> > (ie. the system behaves as if they where not running at all from an
> >> > interactivity pov).
> >> >
> >> >
> >> > P.S: please CC me when replying.
> >> >
> >>
> >> With "NEW_FAIR_SLEEPERS" I can even run 100(!)  "md5sum" task without
> >> any effect on interactivity. (still have not found a number of tasks
> >> needed to make the system unresponsive as with 8 with
> >> "NO_NEW_FAIR_SLEEPERS".
> >
> > Can you try the latest -tip tree please:
> >
> >  http://people.redhat.com/mingo/tip.git/README
> >
> > There we default to FAIR_SLEEPERS + GENTLE_FAIR_SLEEPERS - which should
> > give much of the new-fair-sleepers advantage.
> 
> OK, with this kernel it works fine (can spam the system with md5sum 
> tasks and the desktop is still responsive).
>
> Was able to use the system with 129 "md5sum /dev/urandom" running.

ok, great!

Those changes are in Linus's latest tree as well.

	Ingo
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