linux-kernel - Re: [PATCH 2/2] memcg, vmscan: Fix forced scan of anonymous pages

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Date:	Thu, 31 Jul 2014 11:38:35 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Jerome Marchand <jmarchan@...hat.com>, linux-mm@...ck.org
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH 2/2] memcg, vmscan: Fix forced scan of anonymous pages

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On 07/31/2014 07:49 AM, Jerome Marchand wrote:
> When memory cgoups are enabled, the code that decides to force to
> scan anonymous pages in get_scan_count() compares global values
> (free, high_watermark) to a value that is restricted to a memory
> cgroup (file). It make the code over-eager to force anon scan.
> 
> For instance, it will force anon scan when scanning a memcg that
> is mainly populated by anonymous page, even when there is plenty of
> file pages to get rid of in others memcgs, even when swappiness ==
> 0. It breaks user's expectation about swappiness and hurts
> performance.
> 
> This patch make sure that forced anon scan only happens when there
> not enough file pages for the all zone, not just in one random
> memcg.
> 
> Signed-off-by: Jerome Marchand <jmarchan@...hat.com>

That fix is a lot smaller than I thought it would be. Nice.

Reviewed-by: Rik van Riel <riel@...hat.com>

- -- 
All rights reversed
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