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From: Shakeel Butt To: Matt Fleming Cc: Andrew Morton , Jens Axboe , Minchan Kim , Sergey Senozhatsky , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@cloudflare.com, Matt Fleming , roman.gushchin@linux.dev Subject: Re: [RFC PATCH 0/1] mm: Reduce direct reclaim stalls with RAM-backed swap Message-ID: References: <20260303115358.1323188-1-matt@readmodwrite.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 593488000A X-Stat-Signature: ujtx8bmg3xjq3uqk7514jmtbyahdumzf X-Rspam-User: X-HE-Tag: 1772578069-680134 X-HE-Meta: U2FsdGVkX19aLUOFUJo6XtiIc6+iJAgr9o6oG6ym81fH/9RlAb2r1vkW8qPsHws9n3zpDbh3gF4KyxvZvjP66zbTpjbgMN+ls41q18xqFyP+N0lEuHJM4vNJB66oahEewdkKRz8hQGwsqr+pyCb/nKYOmBOuomvZh844n1N7+1PhH+nghNEOBXWoJzc2gwDYRDaqOOq1PpygnJ6I5YEzQOpynjjestpVrI7iJbGCi/Q3ZrbL0HEEUTP/+Oh0CNlw8jV77KSo6bP87BNFB6Eua/MZ2hUB4QRtT3t0D7bc6e6NOQNfWGBuWXQiA2s3bS9kOIC2KuomCtxrT5kefjh4W+tkCGNJWm+JLKCScXJALaJP3kWjVrncj78cpA9XU7WUOszbNJYxPNiwogQZo3h4mOWT+LQXDTllFeC/bzIJ2oCOMO3ECSmN6S8wobIylYbTFSGZFEwgPLUGB74PG5wLsAIV18AfNHztls0sG/HyWB9Jkl4PPCtybMTge+QqeAbRg2UgRGJi8c2flZIuA7zXbzp4yiUqrTWNlCEuZhxWhq1f/Y/yY35aRDQYbKX+Pp2Gw1EVBj8uZDHSuVVZMTB5XakuOK1KfGuqEBVZfqWsi8dhDaOpqDzaIsX9J4OIiHNqmoR/f2z4kpjanFjqJuMLtVxlMwGVVgt+MGKh+J3O+DmPj0R+TZQK4FmQ8hK07oIKF+frifCwfKI93hBKE1XiXmEpjXf/UMtkhmxWpxP1JRyArznfx3Q508xbBQAaJAbRqTfpo1O2JF6eSk5hyrw3/4rLcofXxaIDBr8KyCzmZAvCvVGM7fBiZncs5ZQz6d+J+WfTk2FnO7qRVqrCy6EydsvEyZMIUJY75DJUxb+FB7y0qls5VnT7RGozcXu+lhaCg5NKObdqyTWka3B59fJ20gGo0qDKRfXoF8Q1VrY8jKHNZNrxIUp3EZOATYEO7h5w9F4ohZ7AbFA89/Odk5g GpLwkK6u Z34alm7v3s/3q6TkCHXHXzeOzssDv2K+JJCATZB9TbcY1rj5vIY9kBmBofKFpewLK9FSFJ5HWSJ11hxekgqTETY1xMr4L2/I1ynYmX0nTggDKuNQSMJNQogHknDUNGEEm3s0MiTE5gioqAOpaCL6W7CY9SBLl7vQkiVSGG7NCbfU1hunHtmXnxD8maCviLeD+vFRkXnIBecwQE+zRE7lWXLzmcTrNTtNorsYlQwQ+ngCF4ZY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 03, 2026 at 07:37:54PM +0000, Matt Fleming wrote: > On Tue, Mar 03, 2026 at 06:59:04AM -0800, Shakeel Butt wrote: > > Hi Matt, > > > > Thanks for the report and one request I have is to avoid cover letter for a > > single patch to avoid partitioning the discussion. > > Noted. > > > Have you tried zswap and if you see similar issues with zswap? > > Yes, we've started experimenting with zswap but that's still in > progress. > > > Over the time we (kernel MM community) have implicitly decided to keep the > > kernel oom-killer very conservative as adding more heuristics in the reclaim/oom > > path makes the kernel more unreliable and punt the aggressiveness of oom-killing > > to the userspace as a policy. All major Linux deployments have started using > > userspace oom-killers like systemd-oomd, Android's LMKD, fb-oomd or some > > internal alternatives. That provides more flexibility to define the > > aggressiveness of oom-killing based on your business needs. > > > > Though userspace oom-killers are prone to reliability issues (oom-killer getting > > stuck in reclaim or not getting enough CPU), so we (Roman) are working on adding > > support for BPF based oom-killer where wen think we can do oom policies more > > reliably. > > > > Anyways, I am wondering if you have tried systemd-oomd or some userspace > > alternative. If you are interested in BPF oom-killer, we can help with that as > > well. > > oomd is also being discussed but so far we haven't experimented with it > yet. > > What's the status of BPF oom-killer: is this the latest? > > https://lore.kernel.org/all/20260127024421.494929-1-roman.gushchin@linux.dev/ Yes this is the latest and I think Roman is planning to send the next version soon.