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b=D+ewexxZq+ooDUyNDi9k2uUo+vxhDfwJVGOzKFDKyu3aC+03hw34dZwLf/bH9XBEY nbely0luL7bgb0/iS8u6oOAa8hwt53wYLfNOCxIvuU8unhF3kUTbMK06OZoUQ/vcqB VDI/4MuzquOKDOGO/FjOVLL7ew0anZutmHnnGHmGgmnetA6LNEwipiWUFkdl3hauTD pOk6J2LlJeKFCc7sJc6G3mKRWvmLkMj35Rke5931vS132QHF+P/tSBYB5Aw/PU/MX1 R1dFiXk26PK7n/87G+D0Cz83m13YCYqxxBUXVKaqfPFHKKCLSJaaqkKVCppOhtxS1R bcr/dTiuraYZQ== From: SeongJae Park To: SeongJae Park Cc: Gregory Price , Matthew Wilcox , lsf-pc@lists.linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Raghavendra K T , Yuanchu Xie , Jonathan Cameron , Kaiyang Zhao , Jiaming Yan , Honggyu Kim Subject: Re: [LSF/MM/BPF TOPIC] DAMON Requirements for Access-aware MM of Future Date: Thu, 2 Jan 2025 10:04:39 -0800 Message-Id: <20250102180439.45429-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250102180019.45333-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D595EA0012 X-Stat-Signature: 6tfepjdz8bbmuyuj6k7cf9m1gabaabw3 X-HE-Tag: 1735841047-281527 X-HE-Meta: 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 WK215529 D2uSFgdpWMhk1ldGaeADqtjVOwLSS4tHswu4w6xS0BMD6kcmBO4K8e4dd6zstO0zYeJzFGDY0/2PLGZMjJydoezMYKPy8BMRjFpSN0iNQYyqVXNbtsSCqqrcpxcAE29ugcTBeNrEwBPkhWhgg6OzJxQ4MkL3j8tRy4VmxKkDV39lvYK8W9yqws7UvsXwrwyqKqzaF1AdyXfz/GTilz3sbd52AsRpE+pbdkhraZM8FBfzry2/dsdmFd0l2k9TUXM/fKGNiD7YfYUhNEzRsit4jGIOg32RsbsuzmrqPJC5cxMhpZr4D6p0rLX1fujuIQg5DjgO7 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 Thu, 2 Jan 2025 10:00:19 -0800 SeongJae Park wrote: > On Thu, 2 Jan 2025 10:22:14 -0500 Gregory Price wrote: > > > On Thu, Jan 02, 2025 at 04:09:38AM +0000, Matthew Wilcox wrote: > > > On Wed, Jan 01, 2025 at 02:20:39PM -0800, SeongJae Park wrote: > > > > Hi all, > > > > > > > > > > > > I find a few interesting and promising projects that aim to do efficient access > > > > pattern-aware memory management of near future, including below (alphabetically > > > > sorted). > > > > > > > > - CXL hotness monitoring unit > > > > (https://lore.kernel.org/20241121101845.1815660-1-Jonathan.Cameron@huawei.com) > > > > - Memory tiering fainess by per-cgroup control of promotion and demotion > > > > (https://lore.kernel.org/20241108190152.3587484-1-kaiyang2@cs.cmu.edu) > > > > - Promotion of unmapped page cache folios > > > > (https://lore.kernel.org/20241210213744.2968-1-gourry@gourry.net) > > > > > > I'm not sure how DAMON can help with this one. As I understand DAMON, > > > it monitors accesses to user addresses. This patchset is trying to solve > > > the problem for file pages which aren't mapped to userspace at all. > > > ie only accessed through read() and write(). > > > > DAMON can monitor physical addresses to, though the mechanism is > > different. > > Thank you for answering this, Gregory. As Gregory explained, users can use > physical address monitoring mode of DAMON for this. For unmapped pages, DAMON > sets and reads PG_idle to check if it is accessed or not. Since PG_idle is > respected by read() and write() use case to my understanding, DAMON should be > able to check accesses to unmapped pages. > > > I haven't assessed this as a solution, yet. > > To quickly see this, I ran below simple test. [...] > the point of this test is that DAMON at least somehow react to accesses for > unmapped pages. Forgot clarifying this point, sorry. My test shows DAMON can detect accesses to unmapped pages, but not asseses if it is feasible as the unmapped pages promotion solution. More works and discussions would be needed for that. Thanks, SJ [...]