diff mbox series

[v8,4/6] ksm: add documentation for ksm zero pages

Message ID 20230522105335.4176-1-yang.yang29@zte.com.cn
State New
Headers
Series ksm: support tracking KSM-placed zero-pages |

Commit Message

Yang Yang May 22, 2023, 10:53 a.m. UTC 
  From: xu xin <xu.xin16@zte.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@zte.com.cn>
Cc: Xiaokai Ran <ran.xiaokai@zte.com.cn>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Cc: Jiang Xuexin <jiang.xuexin@zte.com.cn>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
---
 Documentation/admin-guide/mm/ksm.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

David Hildenbrand May 23, 2023, 9:58 a.m. UTC | #1 
On 22.05.23 12:53, Yang Yang wrote:
> From: xu xin <xu.xin16@zte.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@zte.com.cn>
> Cc: Xiaokai Ran <ran.xiaokai@zte.com.cn>
> Cc: Yang Yang <yang.yang29@zte.com.cn>
> Cc: Jiang Xuexin <jiang.xuexin@zte.com.cn>
> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Cc: David Hildenbrand <david@redhat.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 7626392fe82c..019dc40a0d3c 100644
> --- a/Documentation/admin-guide/mm/ksm.rst
> +++ b/Documentation/admin-guide/mm/ksm.rst
> @@ -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
> +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.

"empty pages" is misleading. You can probably drop the last comment, 
because you repeat that afterwards.

how many zero pages that are still mapped into processes were mapped by 
KSM when deduplicating.


I suggest squashing this patch into #3.
diff mbox series

Patch

diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index 7626392fe82c..019dc40a0d3c 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -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
+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``