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[109.81.21.195]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-439fe20b4dasm5786136f8f.18.2026.03.12.00.18.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 00:18:58 -0700 (PDT) Date: Thu, 12 Mar 2026 08:18:57 +0100 From: Michal Hocko To: Benjamin Lee McQueen Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3] mm/vmpressure: scale window size based on machine memory Message-ID: References: <20260305043038.2176-1-mcq@disroot.org> <31c4680848b833d53b1979b45d5a368d@disroot.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <31c4680848b833d53b1979b45d5a368d@disroot.org> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 19D2B100005 X-Stat-Signature: 6d3hkb6wobus5z3x73a91cbqsxj6k46g X-HE-Tag: 1773299940-990898 X-HE-Meta: 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 anV9VmUz ptt5FaZLp38voSU7O3RrpYG9NHNmXe+ZyIj6QigJPeI686LVEs1GQGgWGb2/7l6qKn6RVp1Av0s3vuaZLxjdmGrpA3ihOFXN2VcC940uVbz8SPnxoL2SMUa5CI48eAC+x4I3lmP0DnXOr0Wx65Z028kdZ8n/ZbjzYI6q38euGbgdIMN6m8Fm5NR48ZYwGt27JbQhI4eM4wO/sIxJmB1JU5rYF53gaS7uFjK0G0xK+p6av0fSSvWc5WpHHOpCj8df79/omKUy1DIZaN16TQkVviqAPAWP4RllfQO6bq7k5B7g13rBIUhuikrCQ29EWI1hpV0UG1Bsy13SXMP6liEOSnU+JCWG+XqArAUDN8e5cc6Mrvns= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri 06-03-26 17:44:08, Benjamin Lee McQueen wrote: > On 2026-03-06 16:52, Michal Hocko wrote: > > On Wed 04-03-26 22:30:38, Benjamin Lee McQueen wrote: > >> the vmpressure window size has been fixed at 512 pages > >> (SWAP_CLUSTER_MAX * 16), ever since the file's inception. a TODO in > >> the file notes that the vmpressure window size should be scaled > >> similarly to vmstat's scaling, via machine size. > >> > >> the problem with fixed window size on large memory systems: > > > > Thank you for this much more detail insight into your thinking. This is > > a good start. I am still missing an overall motivation though. Are you > > trying to address a theoretical concern (the said TODO) or do you have > > any practical workload that generates bogus vmpressure events. > > yes, as i don't personally have a workload that explicitly requires > vmpresssure to not generate bogus events, it is still technically a "bug" > that can still be improved. i believe many legacy systems would benefit > from this as they still use vmpressure notifications. I believe we need some real workloads that have very strong reason to not move to PSI and need this to justify any change in this area. > i agree PSI is the preferred interface, but vmpressure is still used in > other production environments, like Android's LMKD, right? > > -ben -- Michal Hocko SUSE Labs