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Howlett" , David Hildenbrand , Jonathan Corbet , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Randy Dunlap , SJ Park , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , damon@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 5/6] Docs/mm/damon/design: clarify when qt_exceeds increases Date: Mon, 14 Sep 2026 07:19:50 -0700 Message-ID: <20260914141952.91465-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260914141952.91465-1-sj@kernel.org> References: <20260914141952.91465-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 2EB861C000F X-Stat-Signature: yk5q35itp6prrbxaidh3c16u337ef1eb X-Rspam-User: X-HE-Tag: 1789395603-512650 X-HE-Meta: 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 Ed9EvCMZ v0JthkMeqf6uBy8egdHjF+fzVLu16oFMXnz+ND20idHani16+2NX9E3wi3oN5RZgzp5T2U/mnDTGgh9/7q79JszkpUgS7dR1Uq5ODJcfRnqDTkjmac5NAcRUomZ4BdGxFlPsuifXhjjevuK8XbXu1EnjGvz1efpsb8s89DnkaHycxN+vNPlRXJp9KZn9vPuFRU2cTn0f3kfUrvAcIwOVCK6WQYazQxHS+tmeFRwW5J/ZxnikhlF8RqYP9Up7DrqxelVFuReqVbk0suQtsjJMGsHHrmkPHhJFC1U5RlpT2izsYaseSrjC3/jUFPud3RgN/JQBQxVan2h8001U= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Liew Rui Yan 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 Reviewed-by: SJ Park Signed-off-by: SJ Park --- Changes from v1 - v1: https://lore.kernel.org/20260910112255.157012-1-aethernet65535@gmail.com - Collect R-b: From SJ. - Rebase to latest mm-new. 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 cb116a82ff20b..ad09416dfb21a 100644 --- a/Documentation/mm/damon/design.rst +++ b/Documentation/mm/damon/design.rst @@ -696,7 +696,9 @@ 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 -- 2.47.3