linux-kernel - Re: [PATCH 3/3] vmscan: Force kswapd to take notice faster when high-order watermarks are being hit

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Message-Id: <200911032301.59662.elendil@planet.nl>
Date:	Tue, 3 Nov 2009 23:01:50 +0100
From:	Frans Pop <elendil@...net.nl>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, stable@...nel.org,
	linux-kernel@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Sven Geggus <lists@...hsschwanzdomain.de>,
	Karol Lewandowski <karol.k.lewandowski@...il.com>,
	Tobias Oetiker <tobi@...iker.ch>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Stephan von Krawczynski <skraw@...net.com>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [PATCH 3/3] vmscan: Force kswapd to take notice faster when high-order watermarks are being hit

On Monday 02 November 2009, Mel Gorman wrote:
> On Mon, Nov 02, 2009 at 06:32:54PM +0100, Frans Pop wrote:
> > On Monday 02 November 2009, Mel Gorman wrote:
> > > vmscan: Help debug kswapd issues by counting number of rewakeups and
> > > premature sleeps
> > >
> > > There is a growing amount of anedotal evidence that high-order
> > > atomic allocation failures have been increasing since 2.6.31-rc1.
> > > The two strongest possibilities are a marked increase in the number
> > > of GFP_ATOMIC allocations and alterations in timing. Debugging
> > > printk patches have shown for example that kswapd is sleeping for
> > > shorter intervals and going to sleep when watermarks are still not
> > > being met.
> > >
> > > This patch adds two kswapd counters to help identify if timing is an
> > > issue. The first counter kswapd_highorder_rewakeup counts the number
> > > of times that kswapd stops reclaiming at one order and restarts at a
> > > higher order. The second counter kswapd_slept_prematurely counts the
> > > number of times kswapd went to sleep when the high watermark was not
> > > met.
> >
> > What testing would you like done with this patch?
>
> Same reproduction as before except post what the contents of
> /proc/vmstat were after the problem was triggered.

With a representative test I get 0 for kswapd_slept_prematurely.
Tested with .32-rc6 + patches 1-3 + this patch.


View attachment "vmstat" of type "text/plain" (1408 bytes)