Re: [PATCH] mm: vmscan: consistent update to pgsteal and pgscan

Roman Gushchin
2020-05-07T22:29:10Z

On Thu, May 07, 2020 at 01:49:13PM -0700, Shakeel Butt wrote:
> One way to measure the efficiency of memory reclaim is to look at the
> ratio (pgscan+pfrefill)/pgsteal. However at the moment these stats are
> not updated consistently at the system level and the ratio of these are
> not very meaningful. The pgsteal and pgscan are updated for only global
> reclaim while pgrefill gets updated for global as well as cgroup
> reclaim.
>
> Please note that this difference is only for system level vmstats. The
> cgroup stats returned by memory.stat are actually consistent. The
> cgroup's pgsteal contains number of reclaimed pages for global as well
> as cgroup reclaim. So, one way to get the system level stats is to get
> these stats from root's memory.stat but root does not expose that
> interface. Also for !CONFIG_MEMCG machines /proc/vmstat is the only way
> to get these stats. So, make these stats consistent.
>
> Signed-off-by: Shakeel Butt <shakeelb@google.com>

Acked-by: Roman Gushchin <guro@fb.com>

Thanks!