linux-kernel - Re: [Bug #14141] order 2 page allocation failures in iwlagn

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Date:	Fri, 6 Nov 2009 10:51:37 +0100
From:	Frans Pop <elendil@...net.nl>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Chris Mason <chris.mason@...cle.com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Karol Lewandowski <karol.k.lewandowski@...il.com>,
	Mohamed Abbas <mohamed.abbas@...el.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	"John W. Linville" <linville@...driver.com>, linux-mm@...ck.org
Subject: Re: [Bug #14141] order 2 page allocation failures in iwlagn

On Thursday 05 November 2009, Frans Pop wrote:
> On Monday 26 October 2009, Frans Pop wrote:
> > On Tuesday 20 October 2009, Mel Gorman wrote:
> > > I've attached a patch below that should allow us to cheat. When it's
> > > applied, it outputs who called congestion_wait(), how long the
> > > timeout was and how long it waited for. By comparing before and
> > > after sleep times, we should be able to see which of the callers has
> > > significantly changed and if it's something easily addressable.
> >
> > The results from this look fairly interesting (although I may be a bad
> > judge as I don't really know what I'm looking at ;-).
> >
> > I've tested with two kernels:
> > 1) 2.6.31.1: 1 test run
> > 2) 2.6.31.1 + congestion_wait() reverts: 2 test runs
>
> I've taken another look at the data from this debug patch, resulting in
> these graphs: http://people.debian.org/~fjp/tmp/kernel/congestion.pdf
>
> I think the graph may show the reason for the congestion_wait()
> regression. Horizontal axis shows time, vertical axis shows number of
> logged congestion_wait calls per type.

I'm sorry. My initial version had a skewed time axis (showed occurrences 
instead of actual time). I've now uploaded a corrected version:
http://people.debian.org/~fjp/tmp/kernel/congestion.pdf

I've also uploaded a second version that shows cumulative delay per type, 
which probably gives a better insight:
http://people.debian.org/~fjp/tmp/kernel/congestion2.pdf

For both the top chart is without the revert, the bottom one after the 
revert.
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