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b=dQdBVOooaa7gvsHwCnljCEeeqnL5QpFI2pjxdkuOhWGIEotMDtyThVuqfFrInzeuV O4IcwF9shTMX1YwjINUlOxQM2lS0ErJaA8l4N6XfwEg7iOa+zbpSJUoqI5iTMTUSbd YAPdYaOdB00uwiS4P8jHqDvM2yf6sdbPhO04G8+vTPuf36/K/eH0TcOALKwTiQva1o Y3ynfsSnA2nPfOL12U9AGX3Cu6y17fApeKRiqjJU6rl0Q78XLIcJ2nEm1I00E+ont6 F1+qnVYq5go4sNdsolG7zxUHNOZf6ezLtrSp9oy4r6K59hVWDxz2SxfShHjRCFqCDL qSV9vCKFTRzhg== From: SeongJae Park To: SeongJae Park Cc: Yunjeong Mun , honggyu.kim@sk.com, kernel_team@skhynix.com, Ravi Jonnalagadda , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, bijan311@gmail.com, ajayjoshi@micron.com Subject: Re: [RFC PATCH 0/5] mm/damon: Add node_sys_bp quota goal metric for Date: Wed, 11 Feb 2026 22:30:09 -0800 Message-ID: <20260212063009.70556-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260204060641.97191-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 658D38000B X-Rspamd-Server: rspam07 X-Stat-Signature: j96tsfsu5zo6drkhms7qrdy3c59n4sjw X-HE-Tag: 1770877819-777138 X-HE-Meta: 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 2vtxV3Qi jv1ucrOorv7zbt25ss8Mvy9S2A1s/LvtHcsoWFPRMHfM12zIksccXjfzXdxyfPs7hlZHDouMC1C1TKH28ylWukqwUYkJFIB/BOpW3N0PCifUlKhN3+yuxAZ9Ol6ikQ9RdUaAxY3W3syy9f57nUcTFRMxeTWXU6HmlAQFBdw1L5vJ6xFqk247FJPMY31EF5kQo7DZ+43VCuXGMo+mOIW7MIfoIeBjNjyZpvTQnh1krHC2kpIi/imUIljDPLNZ7T+TOQek8HqiAMLWoUY5TiE5QjJa8Evggu6EMyd7+VYSuDhSkB/zKSzAzkCqtb6Lq1GOyNdUTzu3GDcCv9QQ7v258zPN1PGvENvk25AsgjGjVUKRfbtBbjfyT26xDlQfas3gKl09P5HdhEk7DjCfFFgGudEw+4g== 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 Tue, 3 Feb 2026 22:06:40 -0800 SeongJae Park wrote: > On Wed, 4 Feb 2026 11:25:35 +0900 Yunjeong Mun wrote: > > > On Fri, Jan 23, 2026 at 05:50:43PM -0800, SeongJae Park wrote: [...] > > > IIRC, SK hynix people also confused with the behavior when they experimented > > > migrate_{hot,cold} action with NODE_MEM_USED_BP goal based quota auto-tuning, > > > but using only a single scheme that does migration in a single direction. > > > Because this is at least second time it made confusion, if you need, maybe I > > > can try to add a feature for making DAMOS immediately stops after the goal is > > > satisfied. Let me know if such new feature can be useful for you. Cc-ing SK > > > hynix people (Honggyu and Yunjeong) so that they can correct me if my memory is > > > broken, or answer if the new feature I described here can be useful for them. > > > > > > > Yes, you're absolutely right. Currently, esz(effective size) starts from 0 and > > esz gradually increases as `current` approaches `target`. > > Once `current` reaches `target`, `esz` then begins to decrease. > > > > However, we observed that even after `current` hits `target`, > > migration still continues relatively aggressively - because `esz` remains high, > > and it takes time for it to decrease. > > > > To address this, we previously suggested that initializing `esz` at `target` > > (or something suitably large value, rather than 0) and letting it gradually > > decrease as `current` gets closer to `target`. > > This would allow for stronger migration when `current` is far form `target`, > > and gradually weaken migration as `current` approaches `target`. > > > > Such a feature would be useful for us to experiment with tiered memory system :) > > Thank you for confirming, Yunjeong. I now agree this is what really need to be > implemented. And I agree your suggestion makes sense for the use case. I want > to take sufficient time for good design of it, though. I will share update as > soon as I get some idea. I just posted an RFC patch series for this: https://lore.kernel.org/20260212062314.69961-1-sj@kernel.org Thanks, SJ [...]