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[109.81.28.101]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3bb7f02578dsm10423195f8f.62.2025.08.17.12.37.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 17 Aug 2025 12:37:28 -0700 (PDT) Date: Sun, 17 Aug 2025 21:37:27 +0200 From: Michal Hocko To: zhongjinji@honor.com Cc: linux-mm@kvack.org, akpm@linux-foundation.org, rientjes@google.com, shakeel.butt@linux.dev, npache@redhat.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, peterz@infradead.org, dvhart@infradead.org, dave@stgolabs.net, andrealmeid@igalia.com, liam.howlett@oracle.com, liulu.liu@honor.com, feng.han@honor.com Subject: Re: [PATCH v4 2/3] mm/oom_kill: Only delay OOM reaper for processes using robust futexes Message-ID: References: <20250814135555.17493-1-zhongjinji@honor.com> <20250814135555.17493-3-zhongjinji@honor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250814135555.17493-3-zhongjinji@honor.com> On Thu 14-08-25 21:55:54, zhongjinji@honor.com wrote: > From: zhongjinji > > The OOM reaper can quickly reap a process's memory when the system encounters > OOM, helping the system recover. Without the OOM reaper, if a process frozen > by cgroup v1 is OOM killed, the victims' memory cannot be freed, and the > system stays in a poor state. Even if the process is not frozen by cgroup v1, > reaping victims' memory is still meaningful, because having one more process > working speeds up memory release. > > When processes holding robust futexes are OOM killed but waiters on those > futexes remain alive, the robust futexes might be reaped before > futex_cleanup() runs. It would cause the waiters to block indefinitely. > To prevent this issue, the OOM reaper's work is delayed by 2 seconds [1]. > The OOM reaper now rarely runs since many killed processes exit within 2 > seconds. > > Because robust futex users are few, it is unreasonable to delay OOM reap for > all victims. For processes that do not hold robust futexes, the OOM reaper > should not be delayed and for processes holding robust futexes, the OOM > reaper must still be delayed to prevent the waiters to block indefinitely [1]. > > Link: https://lore.kernel.org/all/20220414144042.677008-1-npache@redhat.com/T/#u [1] What has happened to https://lore.kernel.org/all/aJGiHyTXS_BqxoK2@tiehlicka/T/#u ? Generally speaking it would be great to provide a link to previous versions of the patchset. I do not see v3 in my inbox (which is quite messy ATM so I might have easily missed it). -- Michal Hocko SUSE Labs