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Sun, 03 May 2026 07:15:32 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F ([213.147.98.98]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a8eb75fc1sm208853235e9.7.2026.05.03.07.15.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 May 2026 07:15:31 -0700 (PDT) Date: Sun, 3 May 2026 15:15:28 +0100 From: Gregory Price To: Matthew Wilcox Cc: "Ritesh Harjani (IBM)" , linux-fsdevel , Amir Goldstein , Christian Brauner , Jan Kara , lsf-pc , Bharata B Rao , Donet Tom , Aboorva Devarajan , linux-mm@kvack.org, Ojaswin Mujoo Subject: Re: [LSF/MM/BPF BoF Session] Numa-Aware Placement for Page Cache Pages Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: F2B36C0012 X-Stat-Signature: ofsnziwbmxphruk5epjk7eiyueq3ian5 X-Rspam-User: X-HE-Tag: 1777817733-829580 X-HE-Meta: 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 et6hgIcZ EFZ/Wa627t1RV2OTQkzgwkWUOPlO0CgHAhIJGNnwF0N0IjZaKxG7ZHrvQMvspkNA5Tf8pEWtTlGmtswmXRnPr4slggfkfzslXKxxoTxA9taRoVr12Y4ufUouCVfwoNGNH8zK7jXqPCIvxYhTLq/uynkgd5jNCgp7rIRrLZSFu5rwGx/XYWy//e154qiP4nwETfFkP4tKblbtFtpJCbBfUymOYPEWhuHOcB4cVgei9LeEjkkCTA12d3OZygNHm00qpcFTn5rczcGzDRvbj9pj3smdvLXGkKpgTHrYSjVaiKf3KoPxiuMogqd34zViEzzcveUXQs4iTjfmIcrjVJQfkZVADSj3+i9G66KzvXnHAt05R+ti6FCBlEJ/sLXkN5rXXeE2oEjOKM06vA+Zb076nrg9qep0yukYkGl8kSIiYeFNT7KeTnLeAKCYsizqSIbPoxN+c2y4pdUGGpGRwG9AqP5XNlJiJycvtPm6fh3wzuQSiYW0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, May 03, 2026 at 12:00:48AM +0100, Matthew Wilcox wrote: > On Sat, May 02, 2026 at 03:57:19PM +0100, Gregory Price wrote: > > On Thu, Apr 30, 2026 at 02:15:19PM +0100, Matthew Wilcox wrote: > > > Ideally, no, the kernel should observe the task and get it right. > > > > Out of curiosity, a use case i've been exploring is something like > > > > fd = open() > > buf = mmap(fd, ...) > > mbind(buf, device_node) > > /* fault file pages directly onto device memory */ > > Could you be explicit what _kind_ of node you're talking about here? > My initial thought went to something like DAX where the node actually > contains persistent memory and the fd is a reference to some chunk > of that storage. But I don't think that's what you're referring to. > You might be thinking about a presentation of DRAM over the CXL fabric. > Or you might be thinking about memory presented by a graphics card > (perhaps over CXL, perhaps some other way). The meaning of "device > memory" has become thoroughly confused (thanks Jerome!) so I sincerely > don't know what you're talking about. > Ah, I can see how the language has moved over time. But yes a gpu with onboard memory presented as a NUMA node, or some other accelerator where the kernel is responsible for managing its memory (rather than a driver). Probably the use-case needs a bit more consideration before we go dangling new policies off the page cache - just chewing on ideas. ~Gregory