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[109.81.88.63]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-439dae4b860sm5074257f8f.36.2026.03.06.07.52.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Mar 2026 07:52:48 -0800 (PST) Date: Fri, 6 Mar 2026 16:52:47 +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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260305043038.2176-1-mcq@disroot.org> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 43A13140008 X-Stat-Signature: t3y1ue4tbjafexjt65pjykpoy4umubap X-HE-Tag: 1772812370-564544 X-HE-Meta: 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 tpKh+Uxi B9/gzB5toijDpBT2QywA60lQFdHzNVrJjpfO0K7ovmRLljXGgiMYxpZ/NuB/EKIAw233TTZPHPUBx4aY03wPQoAjXGedMTlAn6+ezsI0i7ulKP29ILyqzmuPl2FPMhEGvN9R/kk3Ij6TzDT5eobmrB/h32EdZ+nPXsLALWRQIKpvSPlD9oYuU0DL92trfW8mQdW3riwf5sUcJzF/7nOUsVDvi/oFrf1xeh+8EPvZ0HWDUb0hp8VtXVOCeSbbd2/FwcdAJv4irDze2BvBtjaqe05/3URLS4Iyh+wPYl9FuXPr+E3m/vyg78B77JKAwBoiLGuA5LsdH7sVKAkCWbxygMMH0AHWDYd2TnVPk8Mdh/EdxSuU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Also please note that vmpressure is a legacy notification interface only available in cgroup v1. PSI (via memory.pressure or global /proc/pressure/) is a new/preferred method to measure memory pressure. See more Documentation/accounting/psi.rst -- Michal Hocko SUSE Labs