linux-kernel - Re: [ANNOUNCE] Staircase Deadline cpu scheduler version 0.45

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Message-ID: <20070422091451.GA15913@1wt.eu>
Date:	Sun, 22 Apr 2007 11:14:51 +0200
From:	Willy Tarreau <w@....eu>
To:	Con Kolivas <kernel@...ivas.org>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	ck list <ck@....kolivas.org>, Ingo Molnar <mingo@...e.hu>,
	Mike Galbraith <efault@....de>, Al Boldi <a1426z@...ab.com>,
	Peter Williams <pwil3058@...pond.net.au>,
	Nick Piggin <npiggin@...e.de>, Matt Mackall <mpm@...enic.com>,
	Bill Huey <billh@...ppy.monkey.org>,
	William Lee Irwin III <wli@...omorphy.com>,
	Gene Heskett <gene.heskett@...il.com>
Subject: Re: [ANNOUNCE] Staircase Deadline cpu scheduler version 0.45

On Sun, Apr 22, 2007 at 06:53:58PM +1000, Con Kolivas wrote:
> On Sunday 22 April 2007 18:06, Willy Tarreau wrote:
> > On Sun, Apr 22, 2007 at 05:31:58PM +1000, Con Kolivas wrote:
> > > On Sunday 22 April 2007 17:27, Con Kolivas wrote:
> > > > On Sunday 22 April 2007 17:00, Willy Tarreau wrote:
> > > > > On Sun, Apr 22, 2007 at 02:41:48PM +1000, Con Kolivas wrote:
> > > > > > A significant bugfix for SMP balancing was just posted for the
> > > > > > staircase deadline cpu scheduler which improves behaviour
> > > > > > dramatically on any SMP machine.
> > > > > >
> > > > > > Thanks to Willy Tarreau for noticing likely fault point.
> > > > > >
> > > > > > Also requested was a version in the Makefile so this version of the
> > > > > > patch adds -sd045 to the kernel version.
> > > > >
> > > > > Con, I'm sorry, but it is worse with this one :-(
> > > >
> > > > Well that was quick testing, thanks.
> > > >
> > > > > The lag when typing in xterms is even more noticeable and vmstat
> > > > > output oscillates between 8 and 65, with idle rates around 50%, as
> > > > > you can see below :
> > > > >
> > > > > Renicing X or not does not change anything here.
> > > > >
> > > > > I suspect that the bug you fixed was hiding another one :-/
> > > > > If you want me to test another patch, feel free to ask.
> > >
> > > Just as a debug point could you please try this patch? Thanks.
> >
> > OK, this time, the ocbench took ages to start. They appeared immediately
> > but very few of them (less than 8 out of 64) really started to work. The
> > system remained very responsive and smooth during the test. But I guess
> > I know why : all the load was sent to CPU 0 :
> 
> Shouldn't have affected smp balancing at all, but try this on top of the 
> ontop please? Thanks

Does not change anything. There clearly is a huge regression somewhere :-/
The second CPU is not used by ocbench, and again, out of 64 tasks, only
a small bunch (between 4 and 8) do something.

Con, you should review the changes between 0.44 and 0.45, I think you
introduced a bug which broke fairness while fixing another one.

Willy

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