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

[Johannes Weiner]

On Thu, Jul 31, 2014 at 01:49:45PM +0200, 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>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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