[PATCH v4 3/4] mm/ksm: document smart scan mode

[Stefan Roesch <shr@devkernel.io>]

This adds documentation for the smart scan mode of KSM.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 Documentation/admin-guide/mm/ksm.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index 776f244bdae4..2b38a8bb08af 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -155,6 +155,15 @@ stable_node_chains_prune_millisecs
         scan. It's a noop if not a single KSM page hit the
         ``max_page_sharing`` yet.
 
+smart_scan
+        Historically KSM checked every candidate page for each scan. It did
+        not take into account historic information.  When smart scan is
+        enabled, pages that have previously not been de-duplicated get
+        skipped. How often these pages are skipped depends on how often
+        de-duplication has already been tried and failed. By default this
+        optimization is enabled. The ``pages_skipped`` metric shows how
+        effective the setting is.
+
 The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 
 general_profit
-- 
2.39.3