linux-kernel - Re: [RFC 2/3] mm: add STATIC_PMD_ZERO

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Message-ID: <842b8b5f-fe0b-436b-b8d7-64b215bdf9d9@redhat.com>
Date: Mon, 2 Jun 2025 22:32:55 +0200
From: David Hildenbrand <david@...hat.com>
To: Pankaj Raghav <kernel@...kajraghav.com>, Christoph Hellwig <hch@....de>,
 Pankaj Raghav <p.raghav@...sung.com>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
 Ryan Roberts <ryan.roberts@....com>, Vlastimil Babka <vbabka@...e.cz>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Borislav Petkov <bp@...en8.de>,
 Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
 Zi Yan <ziy@...dia.com>, Mike Rapoport <rppt@...nel.org>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Michal Hocko <mhocko@...e.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Thomas Gleixner <tglx@...utronix.de>, Nico Pache <npache@...hat.com>,
 Dev Jain <dev.jain@....com>, "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, linux-block@...r.kernel.org, willy@...radead.org,
 x86@...nel.org, linux-fsdevel@...r.kernel.org,
 "Darrick J . Wong" <djwong@...nel.org>, mcgrof@...nel.org,
 gost.dev@...sung.com
Subject: Re: [RFC 2/3] mm: add STATIC_PMD_ZERO_PAGE config option

On 02.06.25 22:28, David Hildenbrand wrote:
> On 02.06.25 16:49, Pankaj Raghav wrote:
>> On 6/2/25 07:03, Christoph Hellwig wrote:
>>> Should this say FOLIO instead of PAGE in the config option to match
>>> the symbol protected by it?
>>>
>> I am still discussing how the final implementation should be with David. But I will
>> change the _PAGE to _FOLIO as that is what we would like to expose at the end.
> 
> It's a huge page, represented internally as a folio. No strong opinion,
> as ...
> 
> MMF_HUGE_ZERO_PAGE vs. mm_get_huge_zero_folio vs. get_huge_zero_page vs
> ... :)

Just to add, the existing one is exposed (configurable) to the user through

/sys/kernel/mm/transparent_hugepage/use_zero_page

combined with the implicit size through

/sys/kernel/mm/transparent_hugepage/hpage_pmd_size

-- 
Cheers,

David / dhildenb