From: Liew Rui Yan Date: Sun, 15 Mar 2026 16:29:44 +0000 (-0700) Subject: Docs/mm/damon: document exclusivity of special-purpose modules X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4bdbddb4e482f283b60787b97fc06b3da3fb419c;p=thirdparty%2Flinux.git Docs/mm/damon: document exclusivity of special-purpose modules Add a section in design.rst to explain that DAMON special-purpose kernel modules (LRU_SORT, RECLAIM, STAT) run in an exclusive manner and return -EBUSY if another is already running. Update lru_sort.rst, reclaim.rst and stat.rst by adding cross-references to this exclusivity rule at the end of their respective Example sections. This change is motivated from another discussion [1]. Link: https://lkml.kernel.org/r/20260315162945.80994-1-sj@kernel.org Link: https://lore.kernel.org/damon/20260314002119.79742-1-sj@kernel.org/T/#t [1] Signed-off-by: Liew Rui Yan Reviewed-by: SeongJae Park Signed-off-by: SeongJae Park Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst index 73980bacc3a02..56690646cf398 100644 --- a/Documentation/admin-guide/mm/damon/lru_sort.rst +++ b/Documentation/admin-guide/mm/damon/lru_sort.rst @@ -351,3 +351,8 @@ the LRU-list based page granularity reclamation. :: # echo 400 > wmarks_mid # echo 200 > wmarks_low # echo Y > enabled + +Note that this module (damon_lru_sort) cannot run simultaneously with other +DAMON-based special-purpose modules. Refer to :ref:`DAMON design special +purpose modules exclusivity ` +for more details. diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst index 8eba3da8dcee0..442ac5c647951 100644 --- a/Documentation/admin-guide/mm/damon/reclaim.rst +++ b/Documentation/admin-guide/mm/damon/reclaim.rst @@ -318,6 +318,11 @@ granularity reclamation. :: # echo 200 > wmarks_low # echo Y > enabled +Note that this module (damon_reclaim) cannot run simultaneously with other +DAMON-based special-purpose modules. Refer to :ref:`DAMON design special +purpose modules exclusivity ` +for more details. + .. [1] https://research.google/pubs/pub48551/ .. [2] https://lwn.net/Articles/787611/ .. [3] https://www.kernel.org/doc/html/latest/mm/free_page_reporting.html diff --git a/Documentation/admin-guide/mm/damon/stat.rst b/Documentation/admin-guide/mm/damon/stat.rst index e5a5a2c4f803a..c4b14daeb2dd6 100644 --- a/Documentation/admin-guide/mm/damon/stat.rst +++ b/Documentation/admin-guide/mm/damon/stat.rst @@ -45,6 +45,11 @@ You can enable DAMON_STAT by setting the value of this parameter as ``Y``. Setting it as ``N`` disables DAMON_STAT. The default value is set by ``CONFIG_DAMON_STAT_ENABLED_DEFAULT`` build config option. +Note that this module (damon_stat) cannot run simultaneously with other +DAMON-based special-purpose modules. Refer to :ref:`DAMON design special +purpose modules exclusivity ` +for more details. + .. _damon_stat_aggr_interval_us: aggr_interval_us diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst index 29fff20b3c2a9..dc37402c0fee9 100644 --- a/Documentation/mm/damon/design.rst +++ b/Documentation/mm/damon/design.rst @@ -853,6 +853,10 @@ more detail, please read the usage documents for those (:doc:`/admin-guide/mm/damon/stat`, :doc:`/admin-guide/mm/damon/reclaim` and :doc:`/admin-guide/mm/damon/lru_sort`). +.. _damon_design_special_purpose_modules_exclusivity: + +Note that these modules currently run in an exclusive manner. If one of those +is already running, others will return ``-EBUSY`` upon start requests. Sample DAMON Modules --------------------