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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 Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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