linux-kernel - [PATCH v7 4/6] ksm: add documentation for ksm zero pages

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Date:   Thu, 13 Apr 2023 13:56:35 +0800
From:   Yang Yang <yang.yang29@....com.cn>
To:     akpm@...ux-foundation.org, david@...hat.com
Cc:     yang.yang29@....com.cn, imbrenda@...ux.ibm.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        ran.xiaokai@....com.cn, xu.xin.sc@...il.com, xu.xin16@....com.cn,
        Jiang Xuexin <jiang.xuexin@....com.cn>
Subject: [PATCH v7 4/6] ksm: add documentation for ksm zero pages

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

Add the description of ksm_zero_pages.

When use_zero_pages is enabled, pages_sharing cannot represent how
much memory saved actually by KSM, but the sum of ksm_zero_pages +
pages_sharing does.

Signed-off-by: xu xin <xu.xin16@....com.cn>
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>
---
 Documentation/admin-guide/mm/ksm.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index 60dc42b3a6a8..64e6a13bda74 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -212,6 +212,14 @@ stable_node_chains
         the number of KSM pages that hit the ``max_page_sharing`` limit
 stable_node_dups
         number of duplicated KSM pages
+ksm_zero_pages
+        how many empty pages are sharing the kernel zero page(s) instead
+        of other user pages as it would happen normally. Only meaningful
+        when ``use_zero_pages`` is/was enabled.
+
+When ``use_zero_pages`` is/was enabled, the sum of ``pages_sharing`` +
+``ksm_zero_pages`` represents the actual number of pages saved by KSM.
+if ``use_zero_pages`` has never been enabled, ``ksm_zero_pages`` is 0.
 
 A high ratio of ``pages_sharing`` to ``pages_shared`` indicates good
 sharing, but a high ratio of ``pages_unshared`` to ``pages_sharing``
-- 
2.15.2