linux-kernel - Re: VM issue causing high CPU loads

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Message-ID: <20090826110809.GG10955@csn.ul.ie>
Date:	Wed, 26 Aug 2009 12:08:09 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Yohan <kernel@...an.staff.proxad.net>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: VM issue causing high CPU loads

On Mon, Aug 24, 2009 at 04:21:55PM -0700, Andrew Morton wrote:
> On Mon, 24 Aug 2009 16:23:22 +0200
> Yohan <kernel@...an.staff.proxad.net> wrote:
> 
> > Hi,
> > 
> >     Is someone have an idea for that :
> > 
> >         http://bugzilla.kernel.org/show_bug.cgi?id=14024
> > 
> 
> Please generate a kernel profile to work out where all the CPU tie is
> being spent.  Documentation/basic_profiling.txt is a starting point.
> 

In the absense of a profile, here is a total stab in the dark. Is this a
NUMA machine? If so, is /proc/sys/vm/zone_reclaim_mode set to 1 and does
setting it to 0 help?

This is based on a relatively recent bug where malloc() could stall for
long times with large amounts of CPU usage due to useless scanning in
page reclaim.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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