linux-kernel - Re: [PATCH v5 12/14] mm: add config option for clearing page-extents

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Message-ID: <a1575434-77eb-4358-896a-6d0e62feef4c@redhat.com>
Date: Fri, 11 Jul 2025 13:39:26 +0200
From: David Hildenbrand <david@...hat.com>
To: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, x86@...nel.org
Cc: akpm@...ux-foundation.org, bp@...en8.de, dave.hansen@...ux.intel.com,
 hpa@...or.com, mingo@...hat.com, mjguzik@...il.com, luto@...nel.org,
 peterz@...radead.org, acme@...nel.org, namhyung@...nel.org,
 tglx@...utronix.de, willy@...radead.org, raghavendra.kt@....com,
 boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v5 12/14] mm: add config option for clearing page-extents

On 10.07.25 02:59, Ankur Arora wrote:
> Add CONFIG_CLEAR_PAGE_EXTENT to allow clearing of page-extents
> where architecturally supported.
> 
> This is only available with !CONFIG_HIGHMEM because the intent is to
> use architecture support to clear contiguous extents in a single
> operation (ex. via FEAT_MOPS on arm64, string instructions on x86)
> which excludes any possibility of interspersing kmap()/kunmap().
> 
> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
> ---
>   mm/Kconfig | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 781be3240e21..a74a5e02de28 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -910,6 +910,15 @@ config NO_PAGE_MAPCOUNT
>   
>   endif # TRANSPARENT_HUGEPAGE
>   
> +config CLEAR_PAGE_EXTENT
> +	def_bool y
> +	depends on !HIGHMEM && ARCH_HAS_CLEAR_PAGES
> +	depends on TRANSPARENT_HUGEPAGE || HUGETLBFS
> +
> +	help
> +	  Use architectural support for clear_pages() to zero page-extents.
> +	  This is likely to be faster than zeroing page-at-a-time.
> +

IIRC, adding a help text will make this option be configurable by the 
user, no?

This seems like something we can just keep internal, right?

-- 
Cheers,

David / dhildenb