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Date: Tue, 27 Oct 2009 15:19:05 +0000
From: Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH 2/5] page allocator: Do not allow interrupts to use
	ALLOC_HARDER
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To: Christoph Lameter <cl@linux-foundation.org>
Cc: Stephan von Krawczynski <skraw@ithnet.com>, Frans Pop <elendil@planet.nl>, Jiri Kosina <jkosina@suse.cz>, Sven Geggus <lists@fuchsschwanzdomain.de>, Karol Lewandowski <karol.k.lewandowski@gmail.com>, Tobias Oetiker <tobi@oetiker.ch>, "Rafael J. Wysocki" <rjw@sisk.pl>, David Miller <davem@davemloft.net>, Reinette Chatre <reinette.chatre@intel.com>, Kalle Valo <kalle.valo@iki.fi>, David Rientjes <rientjes@google.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Mohamed Abbas <mohamed.abbas@intel.com>, Jens Axboe <jens.axboe@oracle.com>, "John W. Linville" <linville@tuxdriver.com>, Pekka Enberg <penberg@cs.helsinki.fi>, Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>, Greg Kroah-Hartman <gregkh@suse.de>, Kernel Testers List <kernel-testers@vger.kernel.org>, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "linux-mm@kvack.org" <linux-mm@kvack.org>
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On Fri, Oct 23, 2009 at 10:03:05PM -0400, Christoph Lameter wrote:
> There are now rt dependencies in the page allocator that screw things up?
> 

The rt logic was present before.

> And an rt flag causes the page allocator to try harder meaning it adds
> latency.
> 

The harder term in the flag is a bit misleading. The effect of ALLOC_HARDER
is that the watermark is lower for the task. i.e. a rt task is less likely
to enter direct reclaim than normal tasks so it should have less latency.

> ?
> 
> 

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

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