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SubjectRe: [PATCH v3] mm: Make memory.emin the baseline for utilisation determination
On Tue, Jan 29, 2019 at 02:15:25PM -0500, Chris Down wrote:
> Roman points out that when when we do the low reclaim pass, we scale the
> reclaim pressure relative to position between 0 and the maximum
> protection threshold.
> However, if the maximum protection is based on memory.elow, and
> memory.emin is above zero, this means we still may get binary behaviour
> on second-pass low reclaim. This is because we scale starting at 0, not
> starting at memory.emin, and since we don't scan at all below emin, we
> end up with cliff behaviour.
> This should be a fairly uncommon case since usually we don't go into the
> second pass, but it makes sense to scale our low reclaim pressure
> starting at emin.
> You can test this by catting two large sparse files, one in a cgroup
> with emin set to some moderate size compared to physical RAM, and
> another cgroup without any emin. In both cgroups, set an elow larger
> than 50% of physical RAM. The one with emin will have less page
> scanning, as reclaim pressure is lower.
> Signed-off-by: Chris Down <>
> Suggested-by: Roman Gushchin <>
> Cc: Johannes Weiner <>
> Cc: Andrew Morton <>
> Cc: Michal Hocko <>
> Cc: Tejun Heo <>
> Cc: Roman Gushchin <>
> Cc: Dennis Zhou <>
> Cc:
> Cc:
> Cc:
> Cc:

Acked-by: Roman Gushchin <>


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