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Mercier" Cc: Johannes Weiner , Roman Gushchin , Shakeel Butt , 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 Subject: Re: [PATCH v4] mm: memcg: Use larger batches for proactive reclaim Message-ID: References: <20240206175251.3364296-1-tjmercier@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240206175251.3364296-1-tjmercier@google.com> X-Rspam-User: X-Stat-Signature: furr86qgd9n65huk1dfuyr8swkxdinkt X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 9017312000E X-HE-Tag: 1708371224-761740 X-HE-Meta: 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 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 Tue 06-02-24 17:52:50, 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. The restart cost is amortized over more pages with > larger batch sizes, and becomes a significant component of the runtime > if the batch size is too small. > > 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. > > MGLRU enabled - memcg LRU used > root - full reclaim pages/sec time (sec) > pre-0388536ac291 : 68047 10.46 > post-0388536ac291 : 13742 inf > (reclaim-reclaimed)/4 : 67352 10.51 > > MGLRU enabled - memcg LRU not used > /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 > > MGLRU enabled - memcg LRU not used > /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 > Reviewed-by: Michal Koutný Acked-by: Michal Hocko Sorry, I've missed this version -- Michal Hocko SUSE Labs