Re: [PATCH v2] mm/memcontrol: Export memcg->watermark via sysfs for v2 memcg

["Michal Koutný" <mkoutny@suse.com>]

Hi.

On Fri, May 06, 2022 at 10:09:16PM -0700, Ganesan Rajagopal <rganesan@arista.com> 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.

It'll save some future indirections if the commit messages includes the
argument about multiple readers and purposeful irresetability.

> 
> Signed-off-by: Ganesan Rajagopal <rganesan@arista.com>
> ---
>  Documentation/admin-guide/cgroup-v2.rst |  7 +++++++
>  mm/memcontrol.c                         | 13 +++++++++++++
>  2 files changed, 20 insertions(+)

Besides that it looks useful and correct, feel free to add
Reviewed-by: Michal Koutný <mkoutny@suse.com>