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From:   Yosry Ahmed <yosryahmed@google.com>
Date:   Tue, 10 Oct 2023 12:01:44 -0700
Message-ID: <CAJD7tkamU-rnmw=N+W8Uom1AuK4ADrmW5OxxL8FrFZTxMMP5ag@mail.gmail.com>
Subject: Re: [PATCH v2 0/5] mm: memcg: subtree stats flushing and thresholds
To:     domenico cerasuolo <cerasuolodomenico@gmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Ivan Babrou <ivan@cloudflare.com>, Tejun Heo <tj@kernel.org>,
        =?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>,
        Waiman Long <longman@redhat.com>, kernel-team@cloudflare.com,
        Wei Xu <weixugc@google.com>, Greg Thelen <gthelen@google.com>,
        linux-mm@kvack.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Tue, Oct 10, 2023 at 9:48=E2=80=AFAM domenico cerasuolo
<cerasuolodomenico@gmail.com> wrote:
>
> Il giorno mar 10 ott 2023 alle ore 05:21 Yosry Ahmed
> <yosryahmed@google.com> ha scritto:
> >
> > This series attempts to address shortages in today's approach for memcg
> > stats flushing, namely occasionally stale or expensive stat reads. The
> > series does so by changing the threshold that we use to decide whether
> > to trigger a flush to be per memcg instead of global (patch 3), and the=
n
> > changing flushing to be per memcg (i.e. subtree flushes) instead of
> > global (patch 5).
> >
> > Patch 3 & 5 are the core of the series, and they include more details
> > and testing results. The rest are either cleanups or prep work.
> >
> > This series replaces the "memcg: more sophisticated stats flushing"
> > series [1], which also replaces another series, in a long list of
> > attempts to improve memcg stats flushing. It is not a new version of
> > the same patchset as it is a completely different approach. This is
> > based on collected feedback from discussions on lkml in all previous
> > attempts. Hopefully, this is the final attempt.
> >
> > [1]https://lore.kernel.org/lkml/20230913073846.1528938-1-yosryahmed@goo=
gle.com/
> >
> > v1 -> v2:
> > - Fixed compilation error reported by the kernel robot in patch 4, also
> >   added a missing rcu_read_unlock().
> > - More testing results in the commit message of patch 3.
> >
> > Yosry Ahmed (5):
> >   mm: memcg: change flush_next_time to flush_last_time
> >   mm: memcg: move vmstats structs definition above flushing code
> >   mm: memcg: make stats flushing threshold per-memcg
> >   mm: workingset: move the stats flush into workingset_test_recent()
> >   mm: memcg: restore subtree stats flushing
> >
> >  include/linux/memcontrol.h |   8 +-
> >  mm/memcontrol.c            | 269 +++++++++++++++++++++----------------
> >  mm/vmscan.c                |   2 +-
> >  mm/workingset.c            |  42 ++++--
> >  4 files changed, 185 insertions(+), 136 deletions(-)
> >
> > --
> > 2.42.0.609.gbb76f46606-goog
> >
> >
>
> Hi Yosry,
>
> thanks for this series! We backported it on a 5.19-based kernel and ran i=
t on a
> machine for almost a week now. The goal was to fix a CPU utilization regr=
ession
> caused by memory stats readings, it seems that this series was the last b=
it
> needed to completely fix it and bring CPU utilization to 5.12 levels.
>
> FWIW,
>
> Tested-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>

That's awesome. Thanks for the testing!