Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <27ca0db1-2648-3ea7-3a26-208bc580b72f@redhat.com>
Date:   Tue, 23 May 2023 11:51:09 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.0
Subject: Re: [PATCH v8 2/6] ksm: count all zero pages placed by KSM
Content-Language: en-US
To:     Yang Yang <yang.yang29@zte.com.cn>, akpm@linux-foundation.org
Cc:     imbrenda@linux.ibm.com, jiang.xuexin@zte.com.cn,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        ran.xiaokai@zte.com.cn, xu.xin.sc@gmail.com, xu.xin16@zte.com.cn
References: <202305221842587200002@zte.com.cn>
 <20230522105229.4066-1-yang.yang29@zte.com.cn>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230522105229.4066-1-yang.yang29@zte.com.cn>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 22.05.23 12:52, Yang Yang wrote:
> From: xu xin <xu.xin16@zte.com.cn>
> 
> As pages_sharing and pages_shared don't include the number of zero pages
> merged by KSM, we cannot know how many pages are zero pages placed by KSM
> when enabling use_zero_pages, which leads to KSM not being transparent with
> all actual merged pages by KSM. In the early days of use_zero_pages,
> zero-pages was unable to get unshared by the ways like MADV_UNMERGEABLE so
> it's hard to count how many times one of those zeropages was then unmerged.
> 
> But now, unsharing KSM-placed zero page accurately has been achieved, so we
> can easily count both how many times a page full of zeroes was merged with
> zero-page and how many times one of those pages was then unmerged. and so,
> it helps to estimate memory demands when each and every shared page could
> get unshared.
> 
> So we add ksm_zero_pages under /sys/kernel/mm/ksm/ to show the number
> of all zero pages placed by KSM.
> 
> v7->v8:
> Handle the case when khugepaged replaces a shared zeropage by a THP.
> 

Oh, and just a note, such version comments should go below the "--", 
such that they will automatically get dropped when applying the patch.

(Usually, version information in the cover letter is sufficient :) )

-- 
Thanks,

David / dhildenb