linux-kernel - [PATCH 4/8] Docs/admin-guide/mm/damon/usage: document empty target regions commit behavior

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251026182216.118200-5-sj@kernel.org>
Date: Sun, 26 Oct 2025 11:22:09 -0700
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	David Hildenbrand <david@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Michal Hocko <mhocko@...e.com>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	damon@...ts.linux.dev,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 4/8] Docs/admin-guide/mm/damon/usage: document empty target regions commit behavior

Committing a monitoring target with empty target regions is for keeping
the current monitoring results.  This behavior was introduced by commit
973233600676 ("mm/damon/sysfs: update monitoring target regions for
online input commit").  The behavior is not documented, though.  Update
the usage document for clarifying this behavior.

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index d8a3d6e740b3..9991dad60fcf 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -134,7 +134,8 @@ Users can write below commands for the kdamond to the ``state`` file.
 - ``on``: Start running.
 - ``off``: Stop running.
 - ``commit``: Read the user inputs in the sysfs files except ``state`` file
-  again.
+  again.  Monitoring :ref:`target region <sysfs_regions>` inputs are also be
+  ignored if no target region is specified.
 - ``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
@@ -296,6 +297,11 @@ In the beginning, this directory has only one file, ``nr_regions``.  Writing a
 number (``N``) to the file creates the number of child directories named ``0``
 to ``N-1``.  Each directory represents each initial monitoring target region.
 
+If ``nr_regions`` is zero when committing new DAMON parameters online (writing
+``commit`` to ``state`` file of :ref:`kdamond <sysfs_kdamond>`), the commit
+logic ignores the target regions.  In other words, the current monitoring
+results for the target are preserved.
+
 .. _sysfs_region:
 
 regions/<N>/
-- 
2.47.3