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Mon, 16 Feb 2026 12:18:09 -0500 (EST) Date: Mon, 16 Feb 2026 17:18:04 +0000 From: Kiryl Shutsemau To: Matthew Wilcox Cc: Wenchao Hao , "David Hildenbrand (Arm)" , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Add AnonZero accounting for zero-filled anonymous pages Message-ID: References: <20260214084514.2842745-1-haowenchao22@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: DEE67140008 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: qom5eim5yx9wkewxxyfj495rji6bxqta X-HE-Tag: 1771262293-753920 X-HE-Meta: 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 zshzWmi0 J3STTeHUkI+Xleiixk1kH1FOhOAuuKWGcuhpCALX1e2C9a5dwPZX+Y9yzl6fRTBr4hl+9Lq2WfBAOUou3VOO3fiKhTabUQ5hbtwdC4JoTGuySUfoGZarwE81VZk+m81h2+cv+CHoOow07PqCQlEMjArSTV9CQlPW+3gqrdFeb6bRXp3qL3whmOK31IB1odHvraDutsPDek5ousFcxh5BMzp8Eoo2CBOI+Pq9uLrllN3/CLVt8wlcQRD1hmYZZfvzNnin7OCRAxvs45nfgTxAQXTazoxkedrKF9rU0PXD9pw9steIU763ffpR1yrd69l+tq4tpNGF0ytBJZ3aBWSsCzmByu5nRaWVOnZ/eiVjPH7QcIM80hmdfwlcOFiltIEk5Zj0k9UBx41J3DhcgjhfhNTWIe1CkZkfhtguQjqfLXJPjYvP26jtADeHzapYubM7zL2Hn 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, Feb 16, 2026 at 05:01:51PM +0000, Matthew Wilcox wrote: > On Mon, Feb 16, 2026 at 04:54:05PM +0000, Kiryl Shutsemau wrote: > > What I would like to see in the kernel is a syscall that return the > > memory stats in binary form. Something like > > > > size_t memstat(int pidfd, struct memstat memstatbuf[], size_t n, > > unsigned long flags, unsigned long start, unsigned long end); > > > > The syscall will fill up to n memstatbufs, one per-VMA. What exactly > > filled there defined by flags. The return value is how many memstatbuf > > is populated. The caller can call it multiple times to walk address > > space it is interested in. > > > > We also can have a flag that mirrors smaps_rollup behaviour and collect > > all the data into a single memstatbuf. > > But is that what we want? Let's say a process allocates a 2MB THP, uses > 12kB of it and then forks. A lot. Now all children that haven't called > exec() see the wasted 2036kB. Would we rather have something that scans > (say) the LRU list looking for zero memory? Are describing THP shrinker? :) I don't particular care about original poster use-case. I want to see more scalable way to access memory statistic information in general. smaps is slow, because it collects information user doesn't care about. -- Kiryl Shutsemau / Kirill A. Shutemov