Docs/admin-guide/mm/damon/usage: add intervals_goal directory on the hierarchy

Document DAMON sysfs interface usage for DAMON sampling and aggregation
intervals auto-tuning.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: SeongJae Park <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

Documentation/admin-guide/mm/damon/usage.rst

···
     │ │ │ │ :ref:`0 <sysfs_context>`/avail_operations,operations
     │ │ │ │ │ :ref:`monitoring_attrs <sysfs_monitoring_attrs>`/
     │ │ │ │ │ │ intervals/sample_us,aggr_us,update_us
+    │ │ │ │ │ │ │ intervals_goal/access_bp,aggrs,min_sample_us,max_sample_us
     │ │ │ │ │ │ nr_regions/min,max
     │ │ │ │ │ :ref:`targets <sysfs_targets>`/nr_targets
     │ │ │ │ │ │ :ref:`0 <sysfs_target>`/pid_target
···
 - ``off``: Stop running.
 - ``commit``: Read the user inputs in the sysfs files except ``state`` file
   again.
+- ``update_tuned_intervals``: Update the contents of ``sample_us`` and
+  ``aggr_us`` files of the kdamond with the auto-tuning applied ``sampling
+  interval`` and ``aggregation interval`` for the files.  Please refer to
+  :ref:`intervals_goal section <damon_usage_sysfs_monitoring_intervals_goal>`
+  for more details.
 - ``commit_schemes_quota_goals``: Read the DAMON-based operation schemes'
   :ref:`quota goals <sysfs_schemes_quota_goals>`.
 - ``update_schemes_stats``: Update the contents of stats files for each
···
 
 For more details about the intervals and monitoring regions range, please refer
 to the Design document (:doc:`/mm/damon/design`).
+
+.. _damon_usage_sysfs_monitoring_intervals_goal:
+
+contexts/<N>/monitoring_attrs/intervals/intervals_goal/
+-------------------------------------------------------
+
+Under the ``intervals`` directory, one directory for automated tuning of
+``sample_us`` and ``aggr_us``, namely ``intervals_goal`` directory also exists.
+Under the directory, four files for the auto-tuning control, namely
+``access_bp``, ``aggrs``, ``min_sample_us`` and ``max_sample_us`` exist.
+Please refer to  the :ref:`design document of the feature
+<damon_design_monitoring_intervals_autotuning>` for the internal of the tuning
+mechanism.  Reading and writing the four files under ``intervals_goal``
+directory shows and updates the tuning parameters that described in the
+:ref:design doc <damon_design_monitoring_intervals_autotuning>` with the same
+names.  The tuning starts with the user-set ``sample_us`` and ``aggr_us``.  The
+tuning-applied current values of the two intervals can be read from the
+``sample_us`` and ``aggr_us`` files after writing ``update_tuned_intervals`` to
+the ``state`` file.
 
 .. _sysfs_targets:
 

Documentation/mm/damon/design.rst

···
 That is, assumes 4% (20% of 20%) DAMON-observed access events ratio (source)
 to capture 64% (80% multipled by 80%) real access events (outcomes).
 
+To know how user-space can use this feature via :ref:`DAMON sysfs interface
+<sysfs_interface>`, refer to :ref:`intervals_goal <sysfs_scheme>` part of
+the documentation.
+
 
 .. _damon_design_damos: