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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1755805518; bh=OzNuHG3+NQODJt4XHvrP9emvOj9fQf/i3kdn2NVKDPw=; h=Date:From:To:Cc:Subject:Content-Type; b=IFcvG0Bu0yYZn0jRu4sESeBw/KwmI5WcTbFV03cxPzBdcsPhZh4MVjrJ7TrlzwgIw cGoge+8PRtEvywoKK9jUGyo5cDNw3MgIr8p/IJo4ToVx0Zw9m8ZVURCS43qten/NV0 nLTd5ifMJ6j8dZd9H8lTJTJsH6u5ysKKfGVz2Om8vMfc06LLExhTJNnNF2gnUHvWMW UbDvVMXv7Eabyn3tg9N43ncTQkrPG6jGZgZLps7h/PstClptrn8gSUcuWYLchDXlhh AX3H7mlfOh005RMir+3yBO2/8PsDbucAqoEp7whYYBo1T1TZS2vThu0cFaxtQ79LuU CkDRmIWuSM9vQ== Date: Thu, 21 Aug 2025 12:45:15 -0700 From: Davidlohr Bueso To: Michal Hocko Cc: zhongjinji , akpm@linux-foundation.org, andrealmeid@igalia.com, dvhart@infradead.org, feng.han@honor.com, liam.howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liulu.liu@honor.com, mingo@redhat.com, npache@redhat.com, peterz@infradead.org, rientjes@google.com, shakeel.butt@linux.dev, tglx@linutronix.de Subject: Re: [PATCH v4 2/3] mm/oom_kill: Only delay OOM reaper for processes using robust futexes Message-ID: <20250821194515.ohw7rhgo4peepw63@offworld> Mail-Followup-To: Michal Hocko , zhongjinji , akpm@linux-foundation.org, andrealmeid@igalia.com, dvhart@infradead.org, feng.han@honor.com, liam.howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liulu.liu@honor.com, mingo@redhat.com, npache@redhat.com, peterz@infradead.org, rientjes@google.com, shakeel.butt@linux.dev, tglx@linutronix.de References: <20250818120819.26709-1-zhongjinji@honor.com> <20250820025308.rkqlvauh4dz42oic@offworld> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: DB280120008 X-Stat-Signature: i4e5prggq85fubary9b41zyipd16h15p X-HE-Tag: 1755805520-891088 X-HE-Meta: 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 M0rOr5fW vOeLikh7IoECTbRtGbZIEOdGHKHDXT/6mwGjV77uVmOg26LetWmCNFphjfLkgU0qvFAHNUeOmhiw5q3q72/ZWUShpTxKqAAZHvwT1/YNpCtGUXKySGs33sJa6hN42hyUNCyZWAPNdU0hC4Ma906JyUsN21PkF93pLiejd71bQtu7qTTmSST87CE0t+qrHswO88fx4IZWRUBqj7rT6f4qSl2FKJQDMXFXG2+knF/vnHClSFPJxBpYbCn1sReYdGO7y1kg+ThCM4VBf5hvf3oc2TnZ4jeAahxjK5PMq+SO7URHGLXOWiA5j0pdiAArFfKY5zLa9BArUxmjqriBhnJbTEKmG6WPCaeugjXQ3ETKGPxmzj2I= 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 Thu, 21 Aug 2025, Michal Hocko wrote: >On Tue 19-08-25 19:53:08, Davidlohr Bueso wrote: >> Yeah, relying on time as a fix is never a good idea. I was going to suggest >> skipping the reaping for tasks with a robust list, > >let me reiterate that the purpose of the oom reaper is not an oom >killing process optimization. It is crucial to guarantee a forward >progress on the OOM situation by a) async memory reclaim of the oom >victim and b) unblocking oom selection to a different process after a) >is done. That means that the victim cannot block the oom situation for >ever. Therefore we cannot really avoid tasks with robust futex or any >other user processes without achieving b) at the same time. Yes, which is why I indicated that skipping it was less practical. In the real world, users that care enough to use robust futexes should make sure that their application keep the OOM killer away altogether. Thanks, Davidlohr