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b=jFhQWVq8EzKzmIwAYefphQlZM82G1QoacYIaQqrzJjEkJ8smUiTB7x2X8H4PF4CqV EmIcBSo6fVVTyMyoVWUnCWptsPR7si2Eeuy1YL8glOP/ec7ZgX/g/pU07BZBDxrgjZ rH1GtqasLYCAeJmiNFD5lKiAMfTUF5t9LFSj8bvs= Date: Wed, 7 Feb 2024 15:05:03 -0800 From: Andrew Morton To: Sourav Panda Cc: corbet@lwn.net, gregkh@linuxfoundation.org, rafael@kernel.org, mike.kravetz@oracle.com, muchun.song@linux.dev, rppt@kernel.org, david@redhat.com, rdunlap@infradead.org, chenlinxuan@uniontech.com, yang.yang29@zte.com.cn, tomas.mudrunka@gmail.com, bhelgaas@google.com, ivan@cloudflare.com, pasha.tatashin@soleen.com, yosryahmed@google.com, hannes@cmpxchg.org, shakeelb@google.com, kirill.shutemov@linux.intel.com, wangkefeng.wang@huawei.com, adobriyan@gmail.com, vbabka@suse.cz, Liam.Howlett@Oracle.com, surenb@google.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, weixugc@google.com Subject: Re: [PATCH v7 0/1] mm: report per-page metadata information Message-Id: <20240207150503.ca18b372f899091af5e6c40b@linux-foundation.org> In-Reply-To: <20240129224204.1812062-1-souravpanda@google.com> References: <20240129224204.1812062-1-souravpanda@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C39FE40012 X-Rspam-User: X-Stat-Signature: dacbajk9eggkojye8sa9nu1fb5nkotdh X-Rspamd-Server: rspam01 X-HE-Tag: 1707347109-130933 X-HE-Meta: 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 ykG5d7ID tMEgwp8gSULIigTjQOB+92z5eKcRQ7NUKVCDX1//A9L/E0XK8y7FaYAp551yzTAnYWuXFxFe04v89wmnphH6NCj5JQi8VeG1bAPaLrW00uUlxKfyxm2QTujGCMO98NjnyPu2fciRJd/Z3mjkQgr+dEsDk9nz0/srU6s+n3gu9NsVNLAYRD1o9KVsyd1TfYmKm6DtdmtgR+EEZw3umGBueSinY2Q3+ZIQa6btk7++r7VPayp1AYkIxMl4lza+W9zjvYNtCOhcgSVyjoTTFZXQ8ZqPWZBMJYx/fB3H0jpGW2aAyNyPHxLKa4EQLE0VzO1wnO1L7 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, 29 Jan 2024 14:42:03 -0800 Sourav Panda wrote: > This patch adds two new per-node fields, namely nr_page_metadata and > nr_page_metadata_boot to /sys/devices/system/node/nodeN/vmstat and a > global PageMetadata field to /proc/meminfo. This information can be > used by users to see how much memory is being used by per-page > metadata, which can vary depending on build configuration, machine > architecture, and system use. I'm not seeing why this is very useful. OK, you look at it and it tells you a number, but what action can a user take based upon that number? Please tell us more about the value of this, the use cases, what prompted you to expend effort on this.