[PATCH] Docs/admin-guide/mm/damon/reclaim: document how to disable watermarks

[Jinjie Ruan]

DAMON_RECLAIM runs its scheme only while the free memory rate is
between `wmarks_low` and `wmarks_mid`.

But some users want to reclaim cold pages even while the system has
plenty of free memory, and it is not obvious that the existing
watermarks parameters can already do that. So Document the setup.

Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 Documentation/admin-guide/mm/damon/reclaim.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst
index ec7e3e32b4ac..23fede7d1cdb 100644
--- a/Documentation/admin-guide/mm/damon/reclaim.rst
+++ b/Documentation/admin-guide/mm/damon/reclaim.rst
@@ -193,6 +193,13 @@ DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks the
 watermarks.  In the case, the system falls back to the LRU-list based page
 granularity reclamation logic.
 
+To keep DAMON_RECLAIM always active regardless of the free memory rate, set
+``wmarks_high``, ``wmarks_mid`` and ``wmarks_low`` to ``1000``, ``1000`` and
+``0``, respectively.  Then the reclamation is limited only by ``min_age`` and
+the quotas.  This is useful for reclaiming cold pages even while the system
+has plenty of free memory, e.g., right after an idle virtual machine is
+paused.
+
 sample_interval
 ---------------
 
-- 
2.53.0