linux-kernel - [PATCH v2 5/5] ksm: add zero_pages

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Message-Id: <20221009022349.315482-1-xu.xin16@zte.com.cn>
Date:   Sun,  9 Oct 2022 02:23:49 +0000
From:   xu.xin.sc@...il.com
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        xu xin <xu.xin16@....com.cn>,
        Xiaokai Ran <ran.xiaokai@....com.cn>,
        Yang Yang <yang.yang29@....com.cn>,
        Jiang Xuexin <jiang.xuexin@....com.cn>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>
Subject: [PATCH v2 5/5] ksm: add zero_pages_sharing documentation

From: xu xin <xu.xin16@....com.cn>

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@....com.cn>
Cc: Yang Yang <yang.yang29@....com.cn>
Cc: Jiang Xuexin <jiang.xuexin@....com.cn>
Cc: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: David Hildenbrand <david@...hat.com>
Signed-off-by: xu xin <xu.xin16@....com.cn>
---
 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