linux-kernel - Re: [PATCH 1/5] page allocator: Always wake kswapd when restarting an allocation attempt after direct reclaim failed

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Message-ID: <20091022154913.GQ11778@csn.ul.ie>
Date:	Thu, 22 Oct 2009 16:49:13 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	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>,
	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 1/5] page allocator: Always wake kswapd when restarting
	an allocation attempt after direct reclaim failed

On Thu, Oct 22, 2009 at 05:41:53PM +0300, Pekka Enberg wrote:
> On Thu, Oct 22, 2009 at 5:22 PM, Mel Gorman <mel@....ul.ie> wrote:
> > If a direct reclaim makes no forward progress, it considers whether it
> > should go OOM or not. Whether OOM is triggered or not, it may retry the
> > application afterwards. In times past, this would always wake kswapd as well
> > but currently, kswapd is not woken up after direct reclaim fails. For order-0
> > allocations, this makes little difference but if there is a heavy mix of
> > higher-order allocations that direct reclaim is failing for, it might mean
> > that kswapd is not rewoken for higher orders as much as it did previously.
> >
> > This patch wakes up kswapd when an allocation is being retried after a direct
> > reclaim failure. It would be expected that kswapd is already awake, but
> > this has the effect of telling kswapd to reclaim at the higher order as well.
> >
> > Signed-off-by: Mel Gorman <mel@....ul.ie>
> 
> You seem to have dropped the Reviewed-by tags from me and Christoph
> for this patch.
> 

My apologies. I missed then when going through the old mails.

> >  mm/page_alloc.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index bf72055..dfa4362 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1817,9 +1817,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >        if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
> >                goto nopage;
> >
> > +restart:
> >        wake_all_kswapd(order, zonelist, high_zoneidx);
> >
> > -restart:
> >        /*
> >         * OK, we're below the kswapd watermark and have kicked background
> >         * reclaim. Now things get more complex, so set up alloc_flags according
> > --
> > 1.6.3.3
> >
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > the body to majordomo@...ck.org.  For more info on Linux MM,
> > see: http://www.linux-mm.org/ .
> > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> >
> 

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