linux-kernel - Re: [PATCH v2 1/1] mm: skip mlocked THPs that are underused early in deferred_split

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Message-ID: <bae1831b-decf-46bd-a264-1cf3ccaa64a2@linux.dev>
Date: Mon, 8 Sep 2025 17:27:51 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: David Hildenbrand <david@...hat.com>
Cc: Liam.Howlett@...cle.com, baohua@...nel.org,
 baolin.wang@...ux.alibaba.com, dev.jain@....com,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 lorenzo.stoakes@...cle.com, npache@...hat.com, ryan.roberts@....com,
 usamaarif642@...il.com, ziy@...dia.com, akpm@...ux-foundation.org
Subject: Re: [PATCH v2 1/1] mm: skip mlocked THPs that are underused early in
 deferred_split_scan()



On 2025/9/8 17:12, David Hildenbrand wrote:
> On 08.09.25 11:07, Lance Yang wrote:
>> From: Lance Yang <lance.yang@...ux.dev>
>>
>> When we stumble over a fully-mapped mlocked THP in the deferred shrinker,
>> it does not make sense to try to detect whether it is underused, because
>> try_to_map_unused_to_zeropage(), called while splitting the folio, 
>> will not
>> actually replace any zeroed pages by the shared zeropage.
>>
>> Splitting the folio in that case does not make any sense, so let's not 
>> even
>> scan to check if the folio is underused.
>>
>> Suggested-by: David Hildenbrand <david@...hat.com>
> 
> Feel free to drop that, I only tweaked you description :)

Well, I'd actually prefer to keep it. Thanks for setting me straight on
try_to_map_unused_to_zeropage() ;p


> 
> Acked-by: David Hildenbrand <david@...hat.com>

Cheers,
Lance