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[109.81.94.157]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a79bc820e3dsm528650066b.194.2024.07.18.00.21.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jul 2024 00:21:41 -0700 (PDT) Date: Thu, 18 Jul 2024 09:21:40 +0200 From: Michal Hocko To: Johannes Weiner Cc: David Finkel , Tejun Heo , Muchun Song , Andrew Morton , core-services@vimeo.com, Jonathan Corbet , Roman Gushchin , Shuah Khan , Zefan Li , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Shakeel Butt Subject: Re: [PATCH] mm, memcg: cg2 memory{.swap,}.peak write handlers Message-ID: References: <20240715203625.1462309-1-davidf@vimeo.com> <20240715203625.1462309-2-davidf@vimeo.com> <20240717170408.GC1321673@cmpxchg.org> <20240717204453.GD1321673@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240717204453.GD1321673@cmpxchg.org> X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 42776140013 X-Stat-Signature: dq3h4n8f6sxjaou4ng7oqu4fcsus4tgk X-HE-Tag: 1721287303-258246 X-HE-Meta: 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 QIkUVYr6 e0flj5+4P2acVmZH9/aOomk0B57Vbx8tIUE1dchtxodoLtmSkI4QImrA3JCr5za6Ked2WY5/iFGWpQ5FvDygTw8DXwpC4Pyz6iAD9sTOQH5s2BRhu+8tBGqGdI66dNvYbrZDk/p2TcOJ1uNQm1P7kqeVp87BXfppXkIQS2Y4JM/EquSKkMWwAah67X2v309hRAZpbkajpzH8f8bOWC25sCNAvip1237/Z9W/T+B2ueVaBiiaZy5Eg8ogpaS1GhfqaWR1MK7v+VgsUw6H5rfnul49U87ELWfib1/JR 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 Wed 17-07-24 16:44:53, Johannes Weiner wrote: [...] > The problem is that once global resetting is allowed, it makes the > number reported in memory.peak unreliable for everyone. You just don't > know, and can't tell, if somebody wrote to it recently. It's not too > much of a leap to say this breaks the existing interface contract. I do not remember any bug reports from v1 where there was a max usage misreported because of uncoordinated value reseting. So while you are right that this is theoretically possible I am not convinced this is a real problem in practice. On the other hand it seems there is a wider agreement this shouldn't be added to v2 and I do respect that. > You have to decide whether the above is worth implementing. But my > take is that the downsides of the simpler solution outweigh its > benefits. While this seems quite elegant I am not convinced this is really worth the additional code for a metric like peak memory consumption which is a very limited metric in a presence of memory reclaim. Thanks! -- Michal Hocko SUSE Labs