Re: VM issue causing high CPU loads

From: Mel Gorman
Date: Wed Aug 26 2009 - 07:08:18 EST

On Mon, Aug 24, 2009 at 04:21:55PM -0700, Andrew Morton wrote:
> On Mon, 24 Aug 2009 16:23:22 +0200
> Yohan <kernel@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > Is someone have an idea for that :
> >
> >
> >
> 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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