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Date:   Sat, 2 Dec 2023 11:51:58 +0700
From:   Bagas Sanjaya <bagasdotme@gmail.com>
To:     Yosry Ahmed <yosryahmed@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     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>,
        Michal =?utf-8?Q?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>,
        Domenico Cerasuolo <cerasuolodomenico@gmail.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Linux CGroups <cgroups@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [mm-unstable v4 0/5] mm: memcg: subtree stats flushing and
 thresholds
Message-ID: <ZWq37kuibjnAecxN@archie.me>
References: <20231129032154.3710765-1-yosryahmed@google.com>
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On Wed, Nov 29, 2023 at 03:21:48AM +0000, Yosry Ahmed wrote:
> 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 then
> changing flushing to be per memcg (i.e. subtree flushes) instead of
> global (patch 5).
>=20
> 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.
>=20
> 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.
>=20
> There was a reported regression in v2 [2] for will-it-scale::fallocate
> benchmark. I believe this regression should not affect production
> workloads. This specific benchmark is allocating and freeing memory
> (using fallocate/ftruncate) at a rate that is much faster to make actual
> use of the memory. Testing this series on 100+ machines running
> production workloads did not show any practical regressions in page
> fault latency or allocation latency, but it showed great improvements in
> stats read time. I do not have numbers about the exact improvements for
> this series, but combined with another optimization for cgroup v1 [3] we
> see 5-10x improvements. A significant chunk of that is coming from the
> cgroup v1 optimization, but this series also made an improvement as
> reported by Domenico [4].
>=20
> v3 -> v4:
> - Rebased on top of mm-unstable + "workload-specific and memory
>   pressure-driven zswap writeback" series to fix conflicts [5].
>=20
> v3: https://lore.kernel.org/all/20231116022411.2250072-1-yosryahmed@googl=
e.com/
>=20
> [1]https://lore.kernel.org/lkml/20230913073846.1528938-1-yosryahmed@googl=
e.com/
> [2]https://lore.kernel.org/lkml/202310202303.c68e7639-oliver.sang@intel.c=
om/
> [3]https://lore.kernel.org/lkml/20230803185046.1385770-1-yosryahmed@googl=
e.com/
> [4]https://lore.kernel.org/lkml/CAFYChMv_kv_KXOMRkrmTN-7MrfgBHMcK3YXv0dPY=
EL7nK77e2A@mail.gmail.com/
> [5]https://lore.kernel.org/all/20231127234600.2971029-1-nphamcs@gmail.com/
>=20
> 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
>=20
>  include/linux/memcontrol.h |   8 +-
>  mm/memcontrol.c            | 272 +++++++++++++++++++++----------------
>  mm/vmscan.c                |   2 +-
>  mm/workingset.c            |  42 ++++--
>  4 files changed, 188 insertions(+), 136 deletions(-)
>=20

No regressions when booting the kernel with this series applied.

Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>

--=20
An old man doll... just what I always wanted! - Clara

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