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From: Roman Gushchin <roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>
Subject: Re: [PATCH v2] mm/memcontrol: Export memcg->watermark via sysfs for
 v2 memcg
Date: Tue, 10 May 2022 19:48:09 -0700
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To: Ganesan Rajagopal <rganesan-nzgTgzXrdUbQT0dZR+AlfA@public.gmane.org>
Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org

On Fri, May 06, 2022 at 10:09:16PM -0700, Ganesan Rajagopal wrote:
> We run a lot of automated tests when building our software and run into
> OOM scenarios when the tests run unbounded. v1 memcg exports
> memcg->watermark as "memory.max_usage_in_bytes" in sysfs. We use this
> metric to heuristically limit the number of tests that can run in
> parallel based on per test historical data.
> 
> This metric is currently not exported for v2 memcg and there is no
> other easy way of getting this information. getrusage() syscall returns
> "ru_maxrss" which can be used as an approximation but that's the max
> RSS of a single child process across all children instead of the
> aggregated max for all child processes. The only work around is to
> periodically poll "memory.current" but that's not practical for
> short-lived one-off cgroups.
> 
> Hence, expose memcg->watermark as "memory.peak" for v2 memcg.
> 
> Signed-off-by: Ganesan Rajagopal <rganesan-nzgTgzXrdUbQT0dZR+AlfA@public.gmane.org>

Acked-by: Roman Gushchin <roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>

I've been asked a couple of times about this feature, so I think it's indeed
useful.

Thank you for adding it!