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Date:   Fri, 13 May 2022 09:19:08 +0800
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Subject: Re: [PATCH v3] mm/khugepaged: sched to numa node when collapse huge
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To:     Andrew Morton <akpm@linux-foundation.org>,
        Peter Xu <peterx@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Yang Shi <shy828301@gmail.com>
References: <20220317065024.2635069-1-maobibo@loongson.cn>
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 <YmrB/7ehG2kj2RMn@xz-m1.local>
 <20220512173620.2f5175c7a321e6ccea6e58e9@linux-foundation.org>
From:   maobibo <maobibo@loongson.cn>
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在 2022/5/13 08:36, Andrew Morton 写道:
> On Thu, 28 Apr 2022 12:34:07 -0400 Peter Xu <peterx@redhat.com> wrote:
> 
>> On Thu, Apr 28, 2022 at 05:17:07PM +0200, David Hildenbrand wrote:
>>> On 17.03.22 07:50, Bibo Mao wrote:
>>>> collapse huge page will copy huge page from general small pages,
>>>> dest node is calculated from most one of source pages, however
>>>> THP daemon is not scheduled on dest node. The performance may be
>>>> poor since huge page copying across nodes, also cache is not used
>>>> for target node. With this patch, khugepaged daemon switches to
>>>> the same numa node with huge page. It saves copying time and makes
>>>> use of local cache better.
>>>>
>>>> With this patch, specint 2006 base performance is improved with 6%
>>>> on Loongson 3C5000L platform with 32 cores and 8 numa nodes.
>>>
>>> If it helps, that's nice as long as it doesn't hurt other cases.
>>>
> 
> Quite a bit of doubtful feedback and we have yet to hear from the
> author.  I'll drop the patch.
> 
> Bibo, please resend at a later time if you feel the patch remains
> desirable.  Please attempt to address the feedback via code changes
> and/or changelogging.
Sorry for the late response, the mail is filtered and I did not notice that. The result is not so obvious after bandwidth is improved between nodes, it is only about 1% improvement for specint2006 for 32 core on my box.

Now I do not see negative effective about this patch unless user wants to keep some cores separated from khugepaged daemon process.


regards
bibo,mao