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Date: Fri, 16 Jan 2009 20:40:49 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>, torvalds@linux-foundation.org,
       linux-kernel@vger.kernel.org
Subject: Re: [git pull] scheduler fixes
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On Wed, 14 Jan 2009 21:24:07 +0100 Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Wed, 2009-01-14 at 12:15 -0800, Andrew Morton wrote:
> > On Sun, 11 Jan 2009 15:43:05 +0100
> > Ingo Molnar <mingo@elte.hu> wrote:
> > 
> > > Please pull the latest sched-fixes-for-linus git tree
> > 
> > In http://bugzilla.kernel.org/show_bug.cgi?id=12309 the reporters have
> > identified what appears to be a sched-related performance regression. 
> > A fairly long-term one - post-2.6.18, perhaps.
> > 
> > Testcase code has been added today.  Could someone please take a look
> > sometime?
> 
> There appear to be two different bug reports in there. One about iowait,
> and one I'm not quite sure what it is about.
> 
> The second thing shows some numbers and a test case, but I fail to see
> what the problem is with it.

I had no problem seeing the problem: a gigantic performance regression
in two CPU-scheduler intensive workloads.

I can see some other problems, too.