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Thu, 10 Sep 2026 04:22:48 -0700 (PDT) Received: from celestia ([2402:1980:885b:4183:b098:c1b9:7033:be8a]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-86152045e8dsm7926904b3a.20.2026.09.10.04.22.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 04:22:47 -0700 (PDT) From: Liew Rui Yan To: Cc: Liew Rui Yan , SJ Park , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Randy Dunlap , damon@lists.linux.dev, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] Docs/mm/damon/design: clarify when qt_exceeds increases Date: Thu, 10 Sep 2026 19:22:31 +0800 Message-ID: <20260910112255.157012-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.55.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 049A01A0008 X-Stat-Signature: 1yeemgubsswpp71my5ojdczanpk3z9j8 X-Rspamd-Server: rspam01 X-HE-Tag: 1789039369-770024 X-HE-Meta: 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 e/okBX0b 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: qt_exceeds counts how many times a scheme's quota has been exceeded. When using the temporal auto-tuning algorithm, the effective size quota becomes zero once the goal is [over-]achieved. In this case, the quotas are still set, so qt_exceeds keeps increasing once per quota reset interval while the goal stays achieved. Clarify this behavior in the design document. Signed-off-by: Liew Rui Yan --- Changes from RFC v1: - RFC v1: https://lore.kernel.org/damon/20260908175105.42558-2-aethernet65535@gmail.com - Simplify the explanation. Do not provide a complete definition of qt_exceeds, but rather explain only the increment condition when using temporal auto-tuning algorithm, simply to prevent users from becoming confused and being unable to find any explanation. --- Documentation/mm/damon/design.rst | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst index d036340dae8a..3f38a3cf68e4 100644 --- a/Documentation/mm/damon/design.rst +++ b/Documentation/mm/damon/design.rst @@ -695,7 +695,9 @@ There are two such tuning algorithms that users can select as they need. fast as possible, using maximum allowed quota, but only for a temporal short time. When the quota is under-achieved, this algorithm keeps tuning quota to a maximum allowed one. Once the quota is [over]-achieved, this sets the - quota zero. Useful for deterministic control required environments. + quota zero. Useful for deterministic control required environments. Note + that the zero quota is a valid quota, and therefore ``qt_exceeds`` :ref:`stat + ` will keep increasing in this case. The goal can be specified with five parameters, namely ``target_metric``, ``target_value``, ``current_value``, ``nid`` and ``path``. The auto-tuning -- 2.55.0