netdev - Re: [PATCH 0/5] Candidate fix for increased number of GFP

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Date:	Fri, 6 Nov 2009 09:24:47 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Tobias Diedrich <ranma+kernel@...edrich.de>,
	Frans Pop <elendil@...net.nl>, Jiri Kosina <jkosina@...e.cz>,
	Sven Geggus <lists@...hsschwanzdomain.de>,
	Karol Lewandowski <karol.k.lewandowski@...il.com>,
	Tobias Oetiker <tobi@...iker.ch>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	David Miller <davem@...emloft.net>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Kalle Valo <kalle.valo@....fi>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mohamed Abbas <mohamed.abbas@...el.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	"John W. Linville" <linville@...driver.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Stephan von Krawczynski <skraw@...net.com>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 0/5] Candidate fix for increased number of GFP_ATOMIC
	failures V2

On Fri, Nov 06, 2009 at 07:03:23AM +0100, Tobias Diedrich wrote:
> Mel Gorman wrote:
> > [No BZ ID] Kernel crash on 2.6.31.x (kcryptd: page allocation failure..)
> > 	This apparently is easily reproducible, particular in comparison to
> > 	the other reports. The point of greatest interest is that this is
> > 	order-0 GFP_ATOMIC failures. Sven, I'm hoping that you in particular
> > 	will be able to follow the tests below as you are the most likely
> > 	person to have an easily reproducible situation.
> 
> I've also seen order-0 failures on 2.6.31.5:
> Note that this is with a one process hogging and mlocking memory and
> min_free_kbytes reduced to 100 to reproduce the problem more easily.
> 

Is that a vanilla, with patches 1-3 applied or both?

> I tried bisecting the issue, but in the end without memory pressure
> I can't reproduce it reliably and with the above mentioned pressure
> I get allocation failures even on 2.6.30.o
> 

To be honest, it's not entirely unexpected with min_free_kbytes set that
low. The system should cope with a certain amount of pressure but with
pressure and a low min_free_kbytes, the system will simply be reacting
too late to free memory in the non-atomic paths.

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