linux-kernel - Re: [RFC PATCH 0/8] Reduce system disruption due to kswapd

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Date:	Sun, 24 Mar 2013 20:00:07 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Mel Gorman <mgorman@...e.de>, Linux-MM <linux-mm@...ck.org>
CC:	Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/8] Reduce system disruption due to kswapd

On 03/17/2013 02:04 PM, Mel Gorman wrote:
> Kswapd and page reclaim behaviour has been screwy in one way or the other
> for a long time. Very broadly speaking it worked in the far past because
> machines were limited in memory so it did not have that many pages to scan
> and it stalled congestion_wait() frequently to prevent it going completely
> nuts. In recent times it has behaved very unsatisfactorily with some of
> the problems compounded by the removal of stall logic and the introduction
> of transparent hugepage support with high-order reclaims.
> 
> There are many variations of bugs that are rooted in this area. One example
> is reports of a large copy operations or backup causing the machine to
> grind to a halt or applications pushed to swap. Sometimes in low memory
> situations a large percentage of memory suddenly gets reclaimed. In other
> cases an application starts and kswapd hits 100% CPU usage for prolonged
> periods of time and so on. There is now talk of introducing features like
> an extra free kbytes tunable to work around aspects of the problem instead
> of trying to deal with it. It's compounded by the problem that it can be
> very workload and machine specific.
> 
> This RFC is aimed at investigating if kswapd can be address these various
> problems in a relatively straight-forward fashion without a fundamental
> rewrite.
> 
> Patches 1-2 limits the number of pages kswapd reclaims while still obeying
> 	the anon/file proportion of the LRUs it should be scanning.

Hi,

patch 1 does not apply (on the top of -next), so I can't test this :(.

thanks,
-- 
js
suse labs
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