Docs/admin-guide/mm/damon/usage: document quota goal metric file

Update DAMON usage document for the quota goal target_metric file.

[sj@kernel.org: fix a typo on the auto-tuning design reference link]
  Link: https://lkml.kernel.org/r/20240221170852.55529-3-sj@kernel.org
Link: https://lkml.kernel.org/r/20240219194431.159606-18-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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

@@ -86,7 +86,7 @@ comma (",").
     │ │ │ │ │ │ │ :ref:`quotas <sysfs_quotas>`/ms,bytes,reset_interval_ms,effective_bytes
     │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
     │ │ │ │ │ │ │ │ :ref:`goals <sysfs_schemes_quota_goals>`/nr_goals
-    │ │ │ │ │ │ │ │ │ 0/target_value,current_value
+    │ │ │ │ │ │ │ │ │ 0/target_metric,target_value,current_value
     │ │ │ │ │ │ │ :ref:`watermarks <sysfs_watermarks>`/metric,interval_us,high,mid,low
     │ │ │ │ │ │ │ :ref:`filters <sysfs_filters>`/nr_filters
     │ │ │ │ │ │ │ │ 0/type,matching,memcg_id
@@ -366,11 +366,11 @@ number (``N``) to the file creates the number of child directories named ``0``
 to ``N-1``.  Each directory represents each goal and current achievement.
 Among the multiple feedback, the best one is used.
 
-Each goal directory contains two files, namely ``target_value`` and
-``current_value``.  Users can set and get any number to those files to set the
-feedback.  User space main workload's latency or throughput, system metrics
-like free memory ratio or memory pressure stall time (PSI) could be example
-metrics for the values.  Note that users should write
+Each goal directory contains three files, namely ``target_metric``,
+``target_value`` and ``current_value``.  Users can set and get the three
+parameters for the quota auto-tuning goals that specified on the :ref:`design
+doc <damon_design_damos_quotas_auto_tuning>` by writing to and reading from each
+of the files.  Note that users should further write
 ``commit_schemes_quota_goals`` to the ``state`` file of the :ref:`kdamond
 directory <sysfs_kdamond>` to pass the feedback to DAMON.