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Sun, 04 Feb 2024 08:17:38 -0800 (PST) MIME-Version: 1.0 References: <20240202233855.1236422-1-tjmercier@google.com> In-Reply-To: <20240202233855.1236422-1-tjmercier@google.com> From: Shakeel Butt Date: Sun, 4 Feb 2024 08:17:25 -0800 Message-ID: Subject: Re: [PATCH v3] mm: memcg: Use larger batches for proactive reclaim To: "T.J. Mercier" Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , Efly Young , android-mm@google.com, yuzhao@google.com, mkoutny@suse.com, Yosry Ahmed , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 136A9100010 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: wepggzes5m1z464jtyaafb1ffb373w7s X-HE-Tag: 1707063459-117832 X-HE-Meta: U2FsdGVkX1/gRqbU7nQSeICEpmeYWmL/h3pXaFSRL6hEzRD9eOzXyWHUafHe2dFhMDWGNNWiIMXYD9WYugdyUpY9QKLvPQGnLPTHUKSyKFeNQEudSydOaaofkol6GMefzSQfTgpGa9QMjTjMVC8hAjklkhDE9LdgzgZUy37KoZWxpGfz+TulyyACv/pZHrqvPYGd7B2C6jadf1wJyZz45A8tBQYmZl3uPHKv+Mbq0icg7UFTT0XdKyx2j6oad9ZvfgTE7IGJS+Lr3SJldwLGUV3bi2ZSLQg5K+2JDMb1NoJ7n39OmEk++YWu0RfTewducOmHxlMvtH/wFEPouvSGE7z1jxi7bR1HCEUTopnrJiymgpDuZckvldP4KbOtznP8UpQv0HQ26sFxIWOgwV6eApKlN+HJOyC1TjOoRLaHuUL3SVjQohtEhCP9p1r6greY7jznpfnnhr9SlCsW/7WqW74iXHVDniQTom3nhLoE0HNZfONStS6zTfYlb2Mgjb75AuIfdhFGeaKJtGgt5mA6OL98faOFfnW67/pVGpmsjhBCoQPSENfm1hcuTkZILUD6sWLZAGpcsuzgx3/crAByO5r/TSTITiUyxje1UgMSQCXmEzO8SpQnrLIrNzhtZoDeWR4jRwvHWkOQLlCbRjjBqU50RCyZAI61WITpTbR/wIZPyJhBxAkjjAz8MaaPjCseTeNDOBHQA2/rffWro/3wsyyqRc+bMfvOdxaAu/bQGAG4PBPeTb4FLqwOg/mNYsm3tBXc0r26cmm+QvpQIhhr5lp7jxNPsT01+kqKscoiWr7Bvuh1AfB3W18T5GBO+NPGqb8rD2FANH990D6d2lj4LfZk4heK+chhR+9Y/JIj7JuqzVAVJ09iFf9e+EnqkqBscmHNX6Lo4RXChP7klZhGRdJs64uDISZQfUKf34xE2oPT7zGoqsIqGQhKnUvMjoASF4cHhbg6Iy1XXaP1IMj Hhw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 2, 2024 at 3:39=E2=80=AFPM T.J. Mercier = wrote: > > Before 388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive > reclaim") we passed the number of pages for the reclaim request directly > to try_to_free_mem_cgroup_pages, which could lead to significant > overreclaim. After 0388536ac291 the number of pages was limited to a > maximum 32 (SWAP_CLUSTER_MAX) to reduce the amount of overreclaim. > However such a small batch size caused a regression in reclaim > performance due to many more reclaim start/stop cycles inside > memory_reclaim. > > Reclaim tries to balance nr_to_reclaim fidelity with fairness across > nodes and cgroups over which the pages are spread. As such, the bigger > the request, the bigger the absolute overreclaim error. Historic > in-kernel users of reclaim have used fixed, small sized requests to > approach an appropriate reclaim rate over time. When we reclaim a user > request of arbitrary size, use decaying batch sizes to manage error while > maintaining reasonable throughput. > > root - full reclaim pages/sec time (sec) > pre-0388536ac291 : 68047 10.46 > post-0388536ac291 : 13742 inf > (reclaim-reclaimed)/4 : 67352 10.51 > > /uid_0 - 1G reclaim pages/sec time (sec) overreclaim (MiB) > pre-0388536ac291 : 258822 1.12 107.8 > post-0388536ac291 : 105174 2.49 3.5 > (reclaim-reclaimed)/4 : 233396 1.12 -7.4 > > /uid_0 - full reclaim pages/sec time (sec) > pre-0388536ac291 : 72334 7.09 > post-0388536ac291 : 38105 14.45 > (reclaim-reclaimed)/4 : 72914 6.96 > > Fixes: 0388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive = reclaim") > Signed-off-by: T.J. Mercier > Reviewed-by: Yosry Ahmed > Acked-by: Johannes Weiner > Acked-by: Shakeel Butt