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

[Rik van Riel]

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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@xxxxxxxxxx>

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

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

- -- 
All rights reversed
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