[PATCH 5/5] ksm: add zero_pages_sharing documentation

[xu . xin . sc]

From: xu xin <xu.xin16@xxxxxxxxxx>

When enabling use_zero_pages, pages_sharing cannot represent how
much memory saved indeed. zero_pages_sharing + pages_sharing does.
add the description of zero_pages_sharing.

Cc: Xiaokai Ran <ran.xiaokai@xxxxxxxxxx>
Cc: Yang Yang <yang.yang29@xxxxxxxxxx>
Cc: Jiang Xuexin <jiang.xuexin@xxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
---
 Documentation/admin-guide/mm/ksm.rst | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index fb6ba2002a4b..484665aa7418 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -162,7 +162,7 @@ The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 pages_shared
         how many shared pages are being used
 pages_sharing
-        how many more sites are sharing them i.e. how much saved
+        how many more sites are sharing them
 pages_unshared
         how many pages unique but repeatedly checked for merging
 pages_volatile
@@ -173,6 +173,14 @@ stable_node_chains
         the number of KSM pages that hit the ``max_page_sharing`` limit
 stable_node_dups
         number of duplicated KSM pages
+zero_pages_sharing
+        how many empty pages are sharing kernel zero page(s) instead of
+        with each other as it would happen normally. only effective when
+        enabling ``use_zero_pages`` knob.
+
+If ``use_zero_pages`` is 0, only ``pages_sharing`` can represents how
+much saved. Otherwise, ``pages_sharing`` + ``zero_pages_sharing``
+represents how much saved actually.
 
 A high ratio of ``pages_sharing`` to ``pages_shared`` indicates good
 sharing, but a high ratio of ``pages_unshared`` to ``pages_sharing``
-- 
2.25.1