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Message-ID: <d9eb6672-788e-414d-8138-37a3038e3c47@linux.alibaba.com>
Date: Fri, 23 Feb 2024 19:01:58 +0800
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Subject: Re: [PATCH] mm, thp: display [never] for defrag when THP is set to
 never
To: David Hildenbrand <david@redhat.com>,
 Yuanhe Shu <xiangzao@linux.alibaba.com>, akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <20240222115323.4925-1-xiangzao@linux.alibaba.com>
 <ec6f2c48-3010-4a02-8f42-fc6b912039cf@redhat.com>
From: Liu Song <liusong@linux.alibaba.com>
In-Reply-To: <ec6f2c48-3010-4a02-8f42-fc6b912039cf@redhat.com>
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在 2024/2/22 20:14, David Hildenbrand 写道:
> On 22.02.24 12:53, Yuanhe Shu wrote:
>> When transparent_hugepage is set to never by cmdline or echo, defrag
>> still show what it used to be and can be modified which makes user
>> confusing whether defrag would take effect.
>>
>> Actually if transparent_hugepage is set to never, defrag will not take
>> effect. Just Display never and remain unchangeable to for defrag when
>> transparent_hugepage is set to never.
>>
>> Suggested-by: Liu Song <liusong@linux.alibaba.com>
>> Signed-off-by: Yuanhe Shu <xiangzao@linux.alibaba.com>
>> ---
>
> No, I don't think we want such a dependency between both options.
>
> You might just end up breaking existing scripts (enable defrag before 
> enabling THP) for no good reason.
>
In certain situations where khugepaged_thread is NULL, it would be more
reasonable for the value of
/sys/kernel/mm/transparent_hugepage/khugepaged/defrag to be 0. The patch
should include a fix for this case.

Thanks