linux-kernel - Re: [PATCH 2/3] page allocator: Do not allow interrupts to use ALLOC

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Message-ID: <20091109101128.GB6657@csn.ul.ie>
Date:	Mon, 9 Nov 2009 10:11:28 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Pavel Machek <pavel@....cz>
Cc:	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, stable@...nel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	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>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Stephan von Krawczynski <skraw@...net.com>,
	kernel-testers@...r.kernel.org
Subject: Re: [PATCH 2/3] page allocator: Do not allow interrupts to use
	ALLOC_HARDER

On Wed, Nov 04, 2009 at 10:01:40AM +0100, Pavel Machek wrote:
> 
> > I hope we can move this to another thread if people would like to remove 
> > this exemption completely instead of talking about this trivial fix, which 
> > I doubt there's any objection to.
> 
> I'm arguing that this "trivial fix" is wrong, and that you should just
> remove those two lines.
> 
> If going into reserves from interrupts hurts, doing that from task
> context will hurt, too. "realtime" task should not be normally allowed
> to "hurt" the system like that.
> 									Pavel

As David points out, it has been the behaviour of the system for 4 years
and removing it should be made as a separate decision and not in the
guise of a fix. In the particular case causing concern, there are a lot
more allocations from interrupt due to network receive than there are
from the activities of tasks with a high priority.

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