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b=bV2Oz3wPh9CI2vgAGfVd43hYzt6c1uvlk7ix0Dq2MmknOdhfzHxfi/W7w31THvoWE ebDtjhVfvO+acPp+9yL7RsNOL5Rnl8eTDIO+Fe1PPIQN6rHL5hOhIDu6621+gzqlv8 H83jxW1Eh7YMuhBvyHR7p5n+lW2MQhJ5AQ04Ynrvyg6TVqawhuYYm2op2HCUbhR+H2 ADXlY4fPPr0KuKg2w4ISnUM2WB9WJk9Mi3a4P8GEh0YgdiHnq8lPBivxcQSSUJYM1z iVyyKP1HFEX+iRR952RqoePaLSF7/UVXRTOuVV/FT7PJh4eTrM7eD2LUyNM9bh8SmF xfMmHCv1XGaSg== From: SJ Park To: Ravi Jonnalagadda Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Jonathan Corbet , Bijan Tabatabai , Ajay Joshi , Honggyu Kim , Yunjeong Mun , Akinobu Mita , Lian Wang , Kunwu Chan Subject: Re: [PATCH] mm/damon: add damos_node_eligible_mem_bp tracepoint Date: Sun, 4 Oct 2026 01:01:10 -0700 Message-ID: <20261004080110.37328-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261003202727.3673-1-ravis.opensrc@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 641D580011 X-Stat-Signature: mj8pckpm55mumjyxax77eg89s1xt3tp8 X-HE-Tag: 1791100878-672595 X-HE-Meta: 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 AD+3HYHh tUtBsD2r4x7sgd1MC06dsupgqANiIehDouWwYDAgumSoliugm+ft5Auz2WBrBePgTEGm5mI/u7jDJz1WMnXC+JokEk4FdWSOCZQu9NMxdn4tj/XgNfoNfGIgqvUNeIWR4/yeke1jvpq3Mw3UbRMZUsgWvxzziH9hxa6XnHHnM1hIePyJNZ3y1PDlGElZS7TDQoP5cfJE8qKYFjvb5sHzKAU/bezbWop1DKGY/MgLRM58HIZzaG63rJIWOsQQqLHLqSaYq53GE5c7VNqGLPnh2UsMUrpWv24Q3a9bZjb12/URLtugKEoWT9+ffqmJJwqwUOUHyeqmolnSfQf3abFXxc+U3DCVjZv1nUQhl+zVTp1tR1gB6Vyem8x8M4PiLSlQy6w2LZ5GetxFUoTb5KffKRW8GQQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Ravi, On Sat, 3 Oct 2026 13:27:27 -0700 Ravi Jonnalagadda wrote: > Add a tracepoint for DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP quota goal > evaluation. The tracepoint fires once per quota-score computation when > the goal metric is DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP, exposing > context_idx, scheme_idx, nid, target_value, and current_value. > current_value is reported as the quota tuning sees it, after the goal's > complement setting is applied. > > The DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP metric expresses node memory > occupancy as basis points of eligible bytes. This information is not > exposed through any existing external interface (perf stat, /proc, or > sysfs), so the tracepoint is the only way for userspace to observe the > target and current eligible-memory basis point values at quota-scoring > time. Thank you for this patch! We have damos_esz tracepoint. Have you considered using it? It doesn't expose the current value, though. I thought it wouldn't be real problem in most cases, but I can show it could be problematic for node_eligible_mem_bp case, as the metric value is not straightforward to see without using DAMON. If you really need to know the current_value, I'm open to add a new tracepoint. But I think it has no reason to make it only eligible_mem_bp specific. How about adding more general purpose tracepoint, and/or update the current_value file [1] under the goal sysfs directory to show the current current_value for all goal types? [1] https://origin.kernel.org/doc/html/latest/admin-guide/mm/damon/usage.html#sysfs-schemes-quota-goals Thanks, SJ [...]