linux-kernel - Re: still getting allocation failures (was Re: [PATCH] vmscan: Stop kswapd waiting on congestion when the min watermark is not being met V2)

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Date:	Wed, 2 Dec 2009 11:32:41 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Tobi Oetiker <tobi@...iker.ch>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Frans Pop <elendil@...net.nl>, Jiri Kosina <jkosina@...e.cz>,
	Sven Geggus <lists@...hsschwanzdomain.de>,
	Karol Lewandowski <karol.k.lewandowski@...il.com>,
	linux-kernel@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Stephan von Krawczynski <skraw@...net.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: still getting allocation failures (was Re: [PATCH] vmscan:
	Stop kswapd waiting on congestion when the min watermark is not
	being met V2)

On Sun, Nov 29, 2009 at 08:42:09AM +0100, Tobi Oetiker wrote:
> Hi Mel,
> 
> Thursday Tobias Oetiker wrote:
> > Hi Mel,
> >
> > Nov 13 Mel Gorman wrote:
> >
> > > The last version has a stupid bug in it. Sorry.
> > >
> > > Changelog since V1
> > >   o Fix incorrect negation
> > >   o Rename kswapd_no_congestion_wait to kswapd_skip_congestion_wait as
> > >     suggested by Rik
> > >
> > > If reclaim fails to make sufficient progress, the priority is raised.
> > > Once the priority is higher, kswapd starts waiting on congestion.  However,
> > > if the zone is below the min watermark then kswapd needs to continue working
> > > without delay as there is a danger of an increased rate of GFP_ATOMIC
> > > allocation failure.
> > >
> > > This patch changes the conditions under which kswapd waits on
> > > congestion by only going to sleep if the min watermarks are being met.
> >
> > I finally got around to test this together with the whole series on
> > 2.6.31.6. after running it for a day I have not yet seen a single
> > order:5 allocation problem ... (while I had several an hour before)
> 
> > for the record, my kernel is now running with the following
> > patches:
> >
> > patch1:Date: Thu, 12 Nov 2009 19:30:31 +0000
> > patch1:Subject: [PATCH 1/5] page allocator: Always wake kswapd when restarting an allocation attempt after direct reclaim failed
> >
> > patch2:Date: Thu, 12 Nov 2009 19:30:32 +0000
> > patch2:Subject: [PATCH 2/5] page allocator: Do not allow interrupts to use ALLOC_HARDER
> >
> > patch3:Date: Thu, 12 Nov 2009 19:30:33 +0000
> > patch3:Subject: [PATCH 3/5] page allocator: Wait on both sync and async congestion after direct reclaim
> >
> > patch4:Date: Thu, 12 Nov 2009 19:30:34 +0000
> > patch4:Subject: [PATCH 4/5] vmscan: Have kswapd sleep for a short interval and double check it should be asleep
> >
> > patch5:Date: Fri, 13 Nov 2009 20:03:57 +0000
> > patch5:Subject: [PATCH] vmscan: Stop kswapd waiting on congestion when the min watermark is not being met V2
> >
> > patch6:Date: Tue, 17 Nov 2009 10:34:21 +0000
> > patch6:Subject: [PATCH] vmscan: Have kswapd sleep for a short interval and double check it should be asleep fix 1
> >
> I have now been running the new kernel for a few days and I am
> sorry to report that about a day after booting the allocation
> failures started showing again. More order:4 instead of order:5 ...
> 

Why has the order changed?

Also, what allocator were you using in 2.6.30 and 2.6.31.6, SLAB or
SLUB? Did you happen to change them when upgrading the kernel?

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