[RFC PATCH v1.1 14/16] Docs/mm/damon/design: document attrs-only monitoring

[SJ Park <sj@kernel.org>]

Update DAMON design document for the attributes only monitoring mode.

Signed-off-by: SJ Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 457d6e8bc7878..6d79e7d69be84 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -316,6 +316,26 @@ Another way to do this for higher accuracy is using :ref:`DAMOS filter
 information in page level.  But, because it is operated in page level, the
 overhead is proportional to the size of the memory.
 
+Data Attributes-only Monitoring
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Data access is the primary monitoring information for DAMON.  Hence it
+:ref:`adjusts <damon_design_data_attrs_monitoring>` regions using the access
+:ref:`counter <damon_design_region_based_sampling>` (``nr_accesses``).  In some
+use cases, however, users may want some of :ref:`attributes
+<damon_design_data_attrs_monitoring>` to be the primary information.
+
+Data attributes-only monitoring mode supports this use case.  For the mode,
+each attribute probe has their priority weight value.  Users can describe by
+what combination of the attributes the primary information is decided, by
+setting the priority weight value.  If the total sum of the weights is not
+zero, the mode is enabled.  The regions adjustment mechanism uses the weighted
+sum of the :ref:`probe hit counts <damon_design_data_attrs_monitoring>` instead
+of ``nr_accesses`` in the case.  When the mode is enabled, access monitoring is
+automatically turned off.  The access counter (``nr_accesses``) will always be
+zero and not updated.  Hence the mode is called Data Attributes "only"
+monitoring.
+
 Dynamic Target Space Updates Handling
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-- 
2.47.3