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[109.81.19.111]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432bd5df96asm43642097f8f.28.2026.01.13.06.11.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Jan 2026 06:11:53 -0800 (PST) Date: Tue, 13 Jan 2026 15:11:52 +0100 From: Michal Hocko To: Mathieu Desnoyers Cc: Andrew Morton , linux-kernel@vger.kernel.org, "Paul E. McKenney" , Steven Rostedt , Masami Hiramatsu , Dennis Zhou , Tejun Heo , Christoph Lameter , Martin Liu , David Rientjes , christian.koenig@amd.com, Shakeel Butt , SeongJae Park , Johannes Weiner , Sweet Tea Dorminy , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Christian Brauner , Wei Yang , David Hildenbrand , Miaohe Lin , Al Viro , linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, Yu Zhao , Roman Gushchin , Mateusz Guzik , Matthew Wilcox , Baolin Wang , Aboorva Devarajan Subject: Re: [PATCH v13 2/3] mm: Fix OOM killer inaccuracy on large many-core systems Message-ID: References: <20260111194958.1231477-1-mathieu.desnoyers@efficios.com> <20260111194958.1231477-3-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4BD44100004 X-Stat-Signature: xxcxdfn83eemumuw1dej7pundwwj7r6u X-HE-Tag: 1768313515-673051 X-HE-Meta: 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 tIRy/mPE brdkoeO67eQYOVcMKyLnJVpvI1MHmb1RAeziH3qtV3LijEFoeIX4BAgCVq4SDbkd9QOMyF+bn0oas/1lmBms53jPy9nk8hl9xPEhlRYjScFSHWgvFK5kbvz0lUrNNq8UQ2G5/5D+/H56sPM1DThxGO04ZOseh7jmo0RU1e9Ae2f7etI1+q+Q8eL+OJ5jRqbw6eAV1UNGNrYZw6ni2jaX/ZcSDNGUpMeLdiGDpV73Fx4A+EV2z084ylHDckyzilNgHm8qgphgt9K7iR94cWTwlLP5uVD6chJBYfhlo4Q1JZHftCtUIFFHRF+3CDtYN0dvjQDKrfjeEmNHb3/9v1Vbb8XNr7vrDofACw5adSlesNOA/7RlUEtyBd1hZvXlwscmBekBmgSAWau5UNuuHo5wRWQIKT38h9ZHaAoK6vL2yKHN+XOg= 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 13-01-26 08:51:45, Mathieu Desnoyers wrote: > On 2026-01-13 04:24, Michal Hocko wrote: [...] > - Introduce new proc files, e.g. > > /proc//rss/approximate > /proc//rss/precise > > Where the "approximate" file would export the following lines for each > page type (MM_FILEPAGES, MM_ANONPAGES, MM_SWAPENTS, MM_SHMPAGES, > allowing future additions): > > > > And "precise" would export lines for each page type: > > > > The key thing here is to have different files to query approximated > vs precise values, so we don't have the overhead of the precise sum > when all we need is an approximation. > > This would expose all the bits and pieces needed to allow userspace to > implement something similar to the 2-pass algorithm I'm proposing for > the OOM killer, but tweaked for other use-cases. > > This proposed ABI is purely hypothetical at this stage. Please let me > know if you have something different in mind. TBH, I am not convinced this is really needed. I would simply use the new more-precise interface for /proc//stat with numbers of potential overhead payed by an increased precision. If we need to revert to low precision then we can do that based on a specific report. > When you mention "highlevel doc", which document do you have in mind ? > Something related to lib/percpu_counter_tree.c or to the /proc ABI ? Documentation/core-api/percpu_counter_tree.rst -- Michal Hocko SUSE Labs