linux-kernel - Re: [PATCH 6/8] fs,xfs: Allow kswapd to writeback pages

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Message-ID: <20100719144311.GS13117@csn.ul.ie>
Date:	Mon, 19 Jul 2010 15:43:11 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 6/8] fs,xfs: Allow kswapd to writeback pages

On Mon, Jul 19, 2010 at 10:20:51AM -0400, Christoph Hellwig wrote:
> On Mon, Jul 19, 2010 at 02:11:28PM +0100, Mel Gorman wrote:
> > As only kswapd and memcg are writing back pages, there should be no
> > danger of overflowing the stack. Allow the writing back of dirty pages
> > in xfs from the VM.
> 
> As pointed out during the discussion on one of your previous post memcg
> does pose a huge risk of stack overflows. 

I remember. This is partially to nudge the memcg people to see where
they currently stand with alleviating the problem.

> In the XFS tree we've already
> relaxed the check to allow writeback from kswapd, and until the memcg
> situation we'll need to keep that check.
> 

If memcg remains a problem, I'll drop these two patches.

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