[PATCH 4/4] Docs/damon/usage: Update for the record feature

[SeongJae Park <sj@kernel.org>]

This commit updates the usage document for the record feature of DAMON.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 22 ++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index c0296c14babf..9973dac7101e 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -34,8 +34,8 @@ the reason, this document describes only the debugfs interface
 debugfs Interface
 =================
 
-DAMON exports four files, ``attrs``, ``target_ids``, ``schemes`` and
-``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.
+DAMON exports five files, ``attrs``, ``target_ids``, ``record``, ``schemes``
+and ``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.
 
 
 Attributes
@@ -74,6 +74,24 @@ check it again::
 Note that setting the target ids doesn't start the monitoring.
 
 
+Record
+------
+
+This debugfs file allows you to record monitored access patterns in a regular
+binary file.  The recorded results are first written in an in-memory buffer and
+flushed to a file in batch.  Users can get and set the size of the buffer and
+the path to the result file by reading from and writing to the ``record`` file.
+For example, below commands set the buffer to be 4 KiB and the result to be
+saved in ``/damon.data``. ::
+
+    # cd <debugfs>/damon
+    # echo "4096 /damon.data" > record
+    # cat record
+    4096 /damon.data
+
+The recording can be disabled by setting the buffer size zero.
+
+
 Schemes
 -------
 
-- 
2.17.1