linux-kernel - Re: [2.6.35-rc1, bug] mm: minute-long livelocks in memory reclaim

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Message-ID: <20100823123339.GI31488@dastard>
Date:	Mon, 23 Aug 2010 22:33:39 +1000
From:	Dave Chinner <david@...morbit.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Wu Fengguang <fengguang.wu@...el.com>, Mel Gorman <mel@....ul.ie>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [2.6.35-rc1, bug] mm: minute-long livelocks in memory reclaim

On Mon, Aug 23, 2010 at 02:23:27AM -0700, David Rientjes wrote:
> On Mon, 23 Aug 2010, Wu Fengguang wrote:
> 
> > > I've been testing parallel create workloads over the weekend, and
> > > I've seen this a couple of times now under 8 thread parallel creates
> > > with XFS. I'm running on an 8p VM with 4GB RAM and a fast disk
> > > subsystem. Basically I am seeing the create rate drop to zero
> > > with all 8 CPUs stuck spinning for up to 2 minutes. 'echo t >
> > > /proc/sysrq-trigger' while this is occurring gives the following
> > > trace for all the fs-mark processes:
.....
> 
> You may be interested in Mel's patchset that he just proposed for -mm 
> which identifies watermark variations on machines with high cpu counts 
> (perhaps even eight, as in this report).  The last patch actually reworks 
> this hunk of the code as well.
> 
> 	http://marc.info/?l=linux-mm&m=128255044912938
> 	http://marc.info/?l=linux-mm&m=128255045312950
> 	http://marc.info/?l=linux-mm&m=128255045012942
> 	http://marc.info/?l=linux-mm&m=128255045612954
> 
> Dave, it would be interesting to see if this fixes your problem.

That looks promising - I'll give it a shot, though my test case is
not really what you'd call reproducable(*) so it might take a
couple of days before I can say whether the issue has gone away or
not.

Cheers,

Dave.

(*) create 100 million inodes in parallel using fsmark, collect and
watch behavioural metrics via PCP/pmchart for stuff out of the
ordinary, and dump stack traces, etc when somthing strange occurs.

-- 
Dave Chinner
david@...morbit.com
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