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

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Message-ID: <niywtremc5kfhs3lenmfxvbiiizyexnaw3m25twedmzovfoeno@lk2o46tfdklk>
Date: Mon, 8 Sep 2025 11:38:24 +0100
From: Kiryl Shutsemau <kirill@...temov.name>
To: Lance Yang <lance.yang@...ux.dev>
Cc: akpm@...ux-foundation.org, david@...hat.com, 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
Subject: Re: [PATCH v2 1/1] mm: skip mlocked THPs that are underused early in
 deferred_split_scan()

On Mon, Sep 08, 2025 at 05:07:41PM +0800, 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.

It makes me think, does KSM follows the same logic as
try_to_map_unused_to_zeropage()?

I cannot immediately find what prevents KSM from replacing zeroed mlocked
folio with ZERO_PAGE().

Hm?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov