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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uoCR0-0000000F3wS-00PC; Tue, 19 Aug 2025 02:50:50 +0000 Date: Tue, 19 Aug 2025 03:50:49 +0100 From: Matthew Wilcox To: Boris Burkov Cc: akpm@linux-foundation.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, kernel-team@fb.com, shakeel.butt@linux.dev, wqu@suse.com, mhocko@kernel.org, muchun.song@linux.dev, roman.gushchin@linux.dev, hannes@cmpxchg.org Subject: Re: [PATCH v3 2/4] mm: add vmstat for cgroup uncharged pages Message-ID: References: <04b3a5c9944d79072d752c85dac1294ca9bee183.1755562487.git.boris@bur.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04b3a5c9944d79072d752c85dac1294ca9bee183.1755562487.git.boris@bur.io> X-Stat-Signature: ssw1473148pt4fokrg9wrhzwnnf3sdo8 X-Rspam-User: X-Rspamd-Queue-Id: 01AAA40002 X-Rspamd-Server: rspam05 X-HE-Tag: 1755571851-889566 X-HE-Meta: U2FsdGVkX18pi48f0L2vXLO8AfeCINgQWpsSrNMbuQH5TO4HkXFivv7XW0pjFcY0h/YicW7hUG94UDizWl9kIpumos9uVww2CvbhBQ5SVCG1OLEvPo1TwCcOnnqUsHkmECi42kVJn30DTjbCf/t1np5tOSrAEtUfWAtF0ZK5lQu2eST1xqBEUyXwNU6cruVHejlXiniwBZcKfANogZ16BS5pnDFGgQoxtFWNxtRp2A3cCRTTCqxWO0iv6loXnum0gqp5QxwPAQJaR6bFMSAfSNqniDUgf47jLnoiKXju2d7gKs9gzOVIhpKqv4h+kTX1WlW3AKs0i1bc18zpcpvzDiPQncrfjgHV3D5Jpk0eUW+VrFS8gB8cKF5DJ8Do96H0ugCZuzhWffOpnS2O33/VjEt7OcOy9Oi5qSbiemtaIf8kGEtfpjKcrPBrcAfE+QIrQ7MqRVWm89xwkvM10Dtt3ALi9Qr/CalFqnbWWuAS/VZc9diuD4bJL7j4UFaMQOcIOp3LPU1Hyn9pqQzXz2hFa/J3aL7O3KKYK1nSILsaCPzs/CmTah2QbSOOVjlC+AYIBfc7v/S+7MzTDlHdTNFHYzzV6LNpdsPIJrl34DDHvDESPZ6ZuDfglK3egFQWJ76nysoNJ0l2Uy35ZFvrfzYBblnSQaZmEX4Uxc5DOt+ltYk4NpybeL4RVV8AOZJTdVd6vYmynz3Af566eRIjE12U4OBaiGySq/J4bj3lqbZlmmaKnU9/S4T4iDl8FAZwfVUFBvsPHsgLJB6V+RS8Ex/Pgw6FQmzoVq1snRVPRt22T90XnIu8FwkThVTuyWEW8I+d4J3UG7KNIDNhr1TVMP7DddowEMRyPK3A1QAOL3zTsOteaxCOCAiJcPqZYyTU6Cb0rL+5OHp/GiSUsTUR/w2ifus0AB0Wy9D6SW2FRc6V/EDM3C+zQCOLiHBdHHCcf53bj+WkVJgKkg+zcpyAWqk TWSCjD2f 80H8I7/HZ4E/ZG2Sh6iKYKKTpy65Qi1haJE3a5OBSNVaumCIVKTdA+Mq4W1ccjI0iNx5CJQHxNgqtb779ppYzmXFDTcHxDiEEbgqWXcNZCtPfxMQZj6AbPmEPmjC3+5+wXlSjULe7Rb3nvOqfdA0BLqCvinS9agz0u9+rB95LcBslcNpKoXI3HKb9DA== 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 Mon, Aug 18, 2025 at 05:36:54PM -0700, Boris Burkov wrote: > Uncharged pages are tricky to track by their essential "uncharged" > nature. To maintain good accounting, introduce a vmstat counter tracking > all uncharged pages. Since this is only meaningful when cgroups are > configured, only expose the counter when CONFIG_MEMCG is set. I don't understand why this is needed. Maybe Shakeel had better reasoning that wasn't captured in the commit message. If they're unaccounted, then you can get a good estimate of them just by subtracting the number of accounted pages from the number of file pages. Sure there's a small race between the two numbers being updated, so you migth be off by a bit.