Document damos_before_apply tracepoint on the usage document.
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
Documentation/admin-guide/mm/damon/usage.rst | 37 ++++++++++++++++----
1 file changed, 30 insertions(+), 7 deletions(-)
diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 282062b6f134..6272cd36590a 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -496,15 +496,24 @@ the files as above. Above is only for an example.
.. _tracepoint:
-Tracepoint for Monitoring Results
-=================================
+Tracepoints for Monitoring Results
+==================================
Users can get the monitoring results via the :ref:`tried_regions
-<sysfs_schemes_tried_regions>` or a tracepoint, ``damon:damon_aggregated``.
-While the tried regions directory is useful for getting a snapshot, the
-tracepoint is useful for getting a full record of the results. While the
-monitoring is turned on, you could record the tracepoint events and show
-results using tracepoint supporting tools like ``perf``. For example::
+<sysfs_schemes_tried_regions>`. The interface is useful for getting a
+snapshot, but it could be inefficient for fully recording all the monitoring
+results. For the purpose, two trace points, namely ``damon:damon_aggregated``
+and ``damon:damos_before_apply``, are provided. ``damon:damon_aggregated``
+provides the whole monitoring results, while ``damon:damos_before_apply``
+provides the monitoring results for regions that each DAMON-based Operation
+Scheme (:ref:`DAMOS <damon_design_damos>`) is gonna be applied. Hence,
+``damon:damos_before_apply`` is more useful for recording internal behavior of
+DAMOS, or DAMOS target access
+:ref:`pattern <damon_design_damos_access_pattern>` based query-like efficient
+monitoring results recording.
+
+While the monitoring is turned on, you could record the tracepoint events and
+show results using tracepoint supporting tools like ``perf``. For example::
# echo on > monitor_on
# perf record -e damon:damon_aggregated &
@@ -527,6 +536,20 @@ counter). Finally the tenth field (``X``) shows the ``age`` of the region
(refer to :ref:`design <damon_design_age_tracking>` for more details of the
counter).
+If the event was ``damon:damos_beofre_apply``, the ``perf script`` output would
+be somewhat like below::
+
+ kdamond.0 47293 [000] 80801.060214: damon:damos_before_apply: ctx_idx=0 scheme_idx=0 target_idx=0 nr_regions=11 121932607488-135128711168: 0 136
+ [...]
+
+Each line of the output represents each monitoring region that each DAMON-based
+Operation Scheme was about to be applied at the traced time. The first five
+fields are as usual. It shows the index of the DAMON context (``ctx_idx=X``)
+of the scheme in the list of the contexts of the context's kdamond, the index
+of the scheme (``scheme_idx=X``) in the list of the schemes of the context, in
+addition to the output of ``damon_aggregated`` tracepoint.
+
+
.. _debugfs_interface:
debugfs Interface (DEPRECATED!)
--
2.25.1
