From 10418f263a5c789417da62b969ca15de3e78bc1f Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Mon, 6 Jan 2025 11:33:47 -0800 Subject: [PATCH] Docs/mm/damon/design: add 'statistics' section DAMOS stats are important feature for tuning of DAMOS-based access-aware system operation, and efficient access pattern monitoring. But not well documented on the design document. Add a section on the document. Link: https://lkml.kernel.org/r/20250106193401.109161-3-sj@kernel.org Signed-off-by: SeongJae Park Cc: Jonathan Corbet Signed-off-by: Andrew Morton --- Documentation/mm/damon/design.rst | 38 +++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst index a577ae40e71c..d0f3bd92ed13 100644 --- a/Documentation/mm/damon/design.rst +++ b/Documentation/mm/damon/design.rst @@ -539,6 +539,44 @@ To know how user-space can set the watermarks via :ref:`DAMON sysfs interface `, refer to :ref:`filters ` part of the documentation. +Statistics +~~~~~~~~~~ + +The statistics of DAMOS behaviors that designed to help monitoring, tuning and +debugging of DAMOS. + +DAMOS accounts below statistics for each scheme, from the beginning of the +scheme's execution. + +- ``nr_tried``: Total number of regions that the scheme is tried to be applied. +- ``sz_trtied``: Total size of regions that the scheme is tried to be applied. +- ``nr_applied``: Total number of regions that the scheme is applied. +- ``sz_applied``: Total size of regions that the scheme is applied. +- ``qt_exceeds``: Total number of times the quota of the scheme has exceeded. + +"A scheme is tried to be applied to a region" means DAMOS core logic determined +the region is eligible to apply the scheme's :ref:`action +`. The :ref:`access pattern +`, :ref:`quotas +`, :ref:`watermarks +`, and :ref:`filters +` that handled on core logic could affect this. +The core logic will only ask the underlying :ref:`operation set +` to do apply the action to the region, so whether the +action is really applied or not is unclear. That's why it is called "tried". + +"A scheme is applied to a region" means the :ref:`operation set +` has applied the action to at least a part of the +region. The :ref:`filters ` that handled by the +operation set, and the types of the :ref:`action ` +and the pages of the region can affect this. For example, if a filter is set +to exclude anonymous pages and the region has only anonymous pages, or if the +action is ``pageout`` while all pages of the region are unreclaimable, applying +the action to the region will fail. + +To know how user-space can read the stats via :ref:`DAMON sysfs interface +`, refer to :ref:s`stats ` part of the +documentation. Regions Walking ~~~~~~~~~~~~~~~