linux-kernel - Re: [PATCH v2 4/4] mm: remove boolean output parameters from folio_pte_batch

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Message-ID: <aGU7axcql69-GRQI@localhost.localdomain>
Date: Wed, 2 Jul 2025 16:00:11 +0200
From: Oscar Salvador <osalvador@...e.de>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, Zi Yan <ziy@...dia.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
	Byungchul Park <byungchul@...com>,
	Gregory Price <gourry@...rry.net>,
	Ying Huang <ying.huang@...ux.alibaba.com>,
	Alistair Popple <apopple@...dia.com>,
	Pedro Falcato <pfalcato@...e.de>, Rik van Riel <riel@...riel.com>,
	Harry Yoo <harry.yoo@...cle.com>, Lance Yang <ioworker0@...il.com>
Subject: Re: [PATCH v2 4/4] mm: remove boolean output parameters from
 folio_pte_batch_ext()

On Wed, Jul 02, 2025 at 12:49:26PM +0200, David Hildenbrand wrote:
> Instead, let's just allow for specifying through flags whether we want
> to have bits merged into the original PTE.
> 
> For the madvise() case, simplify by having only a single parameter for
> merging young+dirty. For madvise_cold_or_pageout_pte_range() merging the
> dirty bit is not required, but also not harmful. This code is not that
> performance critical after all to really force all micro-optimizations.

Seems a bit odd to me to have the dirty-young bit being treat as "one".
You mention that this is done because the only user of it doesn't really
care about dirty vs non-dirty and it's not harmful eitherway, so micro-optimizing
this isn't worth at this moment.

But what if we grop another user which wants to make this distinction and
where it matters dirty vs non-dirty/young vs not-young.
Wouldn't be better to have it separated from the start?

And I'm not talking about micro-optimizing, because that's clear that it
doesn't matter, but for clarity purposes.
It seems a lot more organic/natural/obvious to me.



-- 
Oscar Salvador
SUSE Labs