linux-kernel - Re: [PATCH v8 4/6] ksm: add documentation for ksm zero pages

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Message-ID: <c5cc983f-5e28-6fd3-9ec7-5777a36f686c@redhat.com>
Date:   Tue, 23 May 2023 11:58:25 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Yang Yang <yang.yang29@....com.cn>, akpm@...ux-foundation.org
Cc:     imbrenda@...ux.ibm.com, jiang.xuexin@....com.cn,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        ran.xiaokai@....com.cn, xu.xin.sc@...il.com, xu.xin16@....com.cn
Subject: Re: [PATCH v8 4/6] ksm: add documentation for ksm zero pages

On 22.05.23 12:53, Yang Yang wrote:
> 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 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.

-- 
Thanks,

David / dhildenb