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b=ccD4QCoD+ZGvTQkOsHpnF3wFYsaS+2mPtPs61OKV8jkigWs0rUM4C09vZEaKfUzpy QKF6B5RPPHz2PMzRcUkjrEZdEpJiTOGc3m78Bgfi2C1RE1RwUpcEjaqQyZa322wWTC FvFNcQmk9ngwL3B5TTZXRe6LIC25FDLQjkEatEUIgRbWnorOmWnjnLDgyGdBn65ceK b97LXzRiSQsBLGgEc6AfYS3go0wBaGsd79ZDLokUv17Gs3hjxmlo8w5mZxYWnFQeso /OpZrKXVHAXaBYwm403fhWC2zziEprKcGuYgtGEy2lB9TspjDC3oLdU//v/pBTwBL9 8RGm8dk/yAmjg== From: SeongJae Park To: Bijan Tabatabai Cc: SeongJae Park , Gregory Price , David Hildenbrand , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, bijantabatab@micron.com, venkataravis@micron.com, emirakhur@micron.com, ajayjoshi@micron.com, vtavarespetr@micron.com, damon@lists.linux.dev Subject: Re: [RFC PATCH 1/4] mm/mempolicy: Expose policy_nodemask() in include/linux/mempolicy.h Date: Tue, 17 Jun 2025 11:58:34 -0700 Message-Id: <20250617185834.58000-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: C784A40014 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: uccxhhg4fhk4q3capcuefj35p511m8jr X-HE-Tag: 1750186717-333278 X-HE-Meta: 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 jqmHmFAj 03/DeYcMCxWDoxTQbll7rUrjcaeQ0M9NIzk2vCNHQiKl6oFSdU+wfm85ygV6m3XdNjZTvnQlavnlf9KHu31MEHkWhBc6XvFRmxU0dB3Qm0BUSRrJUfyfoisccrKevHtj42blpZzW+/RAeUeRS60G2hM4rYDaCTyU8o1mDDvGLQGqMH9fMmpawplvS+wUmhVvcPPmW9NIt/e7GkB9uTv1pgIAjppDoikuufduEtNyNBaMrr5FSP8bRiQZ1Zlr3O4f3rYOYfAPZSuj6R9F3+XwreZuyANht8DCa98GoEgJvfL+SqkCCVyXHcrUQwGf1WjMHOtP+SKtvZgLrcZLa0Ixaj0NCP/WwKE9dOVOrVJzbGMf+rYtAnMfVMaoKuaV7OQJgsyPKezA2INKRu2bgl4P99A5zv7uvtFLk7/Gaunwk+9v3ZRbbgWMlB1syvMKxsX0UDIlCL1OUjjVE1omH0lDz7s6wjg== 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, 16 Jun 2025 17:16:16 -0500 Bijan Tabatabai wrote: > Hi Gregory, > > On Mon, Jun 16, 2025 at 12:43 PM Gregory Price wrote: > > > > On Mon, Jun 16, 2025 at 09:16:55AM -0500, Bijan Tabatabai wrote: [...] > > Hate to interject here, Please don't hesitate :) [...] > > I will just say that mempolicy is *extremely* current-task centric - and > > very much allocation-time centric (i.e. the internal workings don't > > really want to consider migration all that much). You'll probably find > > that this project requires rethinking mempolicy's external interfaces in > > general (which is sorely needed anyway). > > > > I think this path to modifying mempolicy to support DAMON is a bit > > ambitious for where mempolicy is at the moment. You may be better off > > duplicating the interleave-weight logic and making some helper functions > > to get the weight data, and then coming back around to generalize it > > later. Thank you for the nice clarification and opinion, Gregory. > > This may be true, but I think I will be able to avoid a lot of this > nastiness with what I need. I am going to try with the mempolicy > approach for the next revision, but if I get too much resistance, I > will probably switch to this approach. I have no strong opinion about use of mempolicy for now, as long as mempolicy folks are fine. Nonetheless, I just wanted to mention Gregory's suggestion also sounds fairly good to me. It would avoid unnecessary coupling of the concepts of allocation-time interleaving and after-allocation migration. Also it feels even more aligned with a potential future extension of this project that we discussed[1]: letting users set multiple target nodes for DAMOS_MIGRATE_{HOT,COLD} with arbitrary weights. [1] https://lore.kernel.org/20250613171237.44776-1-sj@kernel.org Thanks, SJ [...]