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Fri, 1 Aug 2025 21:20:18 +0800 From: zhongjinji To: CC: , , , , , , , , Subject: Re: [PATCH] mm: delay oom_reaper only for the process using robust-futex Date: Fri, 1 Aug 2025 21:20:14 +0800 Message-ID: <20250801132014.5740-1-zhongjinji@honor.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.144.20.219] X-ClientProxiedBy: w001.hihonor.com (10.68.25.235) To a018.hihonor.com (10.68.17.250) X-Rspamd-Queue-Id: 5E08A1C000F X-Stat-Signature: ptsfmyhum3bps71cqhj3xd14nq8qfssr X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1754054423-214396 X-HE-Meta: U2FsdGVkX19R0S2VN4Hu+GWHuSF/kRBf9+iP8mAG8ud5goJ70ogWtc75bR/txBDleEYDohKjZEZA0XyikQ93ypwjaJiR3ge58bxtJvlMN+WRqSifUWyAFiu6J5du+xVaUeEc/5yayB9uyhFdCMc06akkMXHYmQnXWOHF+TXGmj4Xf+dVzaiQH7ncnB2Mhi2Xzdf/n/fhMdrp3XF8zSoyYAkKrvWdl43DdFGSH+LPK/hGr3uSLkQrigV5WZ4w30r80/tNTlHjQW2wEMtN7tR6YcUNkBM+lXuz2B/lnyrj62XYPzD4QBnEkM6tvjwqsFKmrE+o8iNrQKLrltV5/KZVzdnFhwfA09ga78tKzWvYTmtQuX4xL3Pk0nl9YUKRnMP3Bsn2ZAyaOfBG9jOLQEtaQXif6pt4CrHM1O1EfZwZjRtLsUOCGc/NkrEm/+1gNeog3+DJuzXw4iNayEZ+gapXQi9di3mUsAUrMGr+kGG9aKZsUYSiA3dVooKm4gOy8aROq2WM8lOXSwiAjdKwa8WoKZP6AAS7wv8sXx4g+gKKfbQkKGupQf8A2Rc22UNTKvV9Nn+eehQhYP8KUs2Zv/ANQSnLb2zqp01MnPtc5nWZKbJviNEpqtcD4WaUEqwQjSbyITVDHGCXMV3vcEeTiVfKRgIWPlRXhoFjxSynuC4L/vfEl5YtkbgcUQeLe8Ncdp7MdATCQRV9waLwlTlDH/mWfW+zXY2FMGxdVuWs92QLqvdI8tyAH6k1u9UR1Kk+T5hjlg0rUhagRr/J0l4QQ80hJbqDd4ZztiCr+NF222IEWJcXLd7lpXNxVhzgpQ9Ymcn2DsNt3CfkOy7CLDRT31NjRbFYL66V7QusPfLZ5sR1/Nls4UC6XajvFKETalh2qyo7NfH6Doe/XgJrgvLau/gRH21qfiwQnlJHvP1VparWamIMxunxWKehpa0ZwfxF3GpZPmNVrExKky/0/tRdE6t jIjfPZDn jlg7N52ra5MFKvEuad6QUde/O9hdKxXGz1A9xlX/0lPZPM3ZqoMx72xLCf8rdzViW2aPkjqdKiSP36ZSnTYQinOmHAzweGhaBpUza9Tz9eckmXzlHuOKABXJnHKScYae0ZALvx7QVJWSaWAxBE17Yi0h2cFpGwFsj0vF+ 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: Yeah, it is enough time for any process on Android to exit within 2 seconds, so the oom reaper basically does not work. Currently, we have not found any users of robust futex on Android. As we know, adding killed processes to the oom_reaper queue can help free their memory faster. Delaying the oom reaper for all processes might lead to less efficient memory reclamation, which could be undesirable. > >> >> But I noticed that many processes do not use robust-futex, so they do not >> access user-space memory during do_exit and do not run into the problem >> mentioned in that patch. >> >> So, this change delays the oom_reaper only when the process uses >> robust-futex, letting the oom_reaper work properly in more cases. > >The direction seems reasonable. > >> >> +static inline bool exit_may_access_user(struct task_struct *task) >> +{ >> + return task->robust_list || task->compat_robust_list; > >Here I am not sure. This robust_list seems like a per-task list and we >are making a process level decision based on a given task's usage of >robust list. Can we have a scenario where some tasks/threads of a >process does not have robust list and others have? If yes this can cause >similar similar which the original patch tried to solve, right? Yes, we definitely need to check whether all threads have a robust list. Thanks for the reminder. I will include this fix in the next version.