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[109.81.86.254]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-45b7e7d23b7sm25444935e9.1.2025.08.29.00.11.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Aug 2025 00:11:55 -0700 (PDT) Date: Fri, 29 Aug 2025 09:11:51 +0200 From: Michal Hocko To: "Liam R. Howlett" Cc: Shakeel Butt , Lorenzo Stoakes , zhongjinji , rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, liulu.liu@honor.com, feng.han@honor.com Subject: Re: [PATCH v5 2/2] mm/oom_kill: Have the OOM reaper and exit_mmap() traverse the maple tree in opposite order Message-ID: References: <20250825133855.30229-1-zhongjinji@honor.com> <20250825133855.30229-3-zhongjinji@honor.com> <002da86b-4be7-41a1-bb14-0853297c2828@lucifer.local> <6cqsibtttohay7ucs4ncmq6nf7xndtyvc4635i2e5ygjsppua6@7iwkgpp245jf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6cqsibtttohay7ucs4ncmq6nf7xndtyvc4635i2e5ygjsppua6@7iwkgpp245jf> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A2F3B40009 X-Stat-Signature: 3hzbu4h4wrjpkr8qs8tgc1qis7tkc6j1 X-Rspam-User: X-HE-Tag: 1756451517-903907 X-HE-Meta: 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 ujtU0mAA ooLMxFWivXCq/JAR0X4V/fQIPmKSaPPrsHHE80ag3X2CltuXMWv4QW32w4zI/2vXIVhmFWWjYYC0WmbhCWYGtKSiG7hheaINw3oLLHfNiKIRGD13ROMsTaJ5u02/bTv0wIsxrIicZeh7szrbuZsfJt28MyQkg9uZOqzBR+3Sv3Do0kgnIJJhipOOE6b8M5je2P03L/3bi7gZzxyTkbTvdEoLx4xANNJYkXk1X7op7JfrLraWlB2xJjgtRXsZxfuzxHVHswedKOGca3s3PuAAqr91gbHcRYvQVPMQT65wcCegR/cqYSadu6VOr8DOz2pSpvEGcGcnntsUSa5VPN3EQq3g2I2JXcD/Yja/ZPt3I4qd/4Z0= 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 27-08-25 00:12:34, Liam R. Howlett wrote: [...] > > > I'd think using MMF_ to reduce the race > > > would achieve the same goal with less risk - which is why I bring it up. > > > > > > > With MMF_ flag, are you suggesting oom reaper to skip the unmapping of > > the oom-killed process? > > Yes, specifically move the MMF_OOM_SKIP flag to earlier in the exit > path to reduce the possibility of the race/contention. MMF_OOM_SKIP is a "hide from oom killer" flag and that means that as soon as you set it up the next oom killer invocation would kill another task while the current one hasn't freed up the memory yet and therefore you have a potentially pointless kill. -- Michal Hocko SUSE Labs