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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> 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: <31c4680848b833d53b1979b45d5a368d@disroot.org> 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