linux-kernel - Re: [PATCH] memcg: async flush memcg stats from perf sensitive codepaths

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Date:   Mon, 28 Feb 2022 19:46:53 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Ivan Babrou <ivan@...udflare.com>,
        Cgroups <cgroups@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Dao <dqminh@...udflare.com>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] memcg: async flush memcg stats from perf sensitive
 codepaths

On Fri, Feb 25, 2022 at 05:42:57PM -0800, Shakeel Butt <shakeelb@...gle.com> wrote:
> Yes, the right fix would be to optimize the flushing code (but that
> would require more work/time). However I still think letting
> performance critical code paths to skip the sync flush would be good
> in general. So, if the current patch is not to your liking we can
> remove mem_cgroup_flush_stats() from workingset_refault().

What about flushing just the subtree of the memcg where the refault
happens?
It doesn't reduce the overall work and there's still full-tree
cgroup_rstat_lock but it should make the chunks of work smaller
durations more regular.


Michal