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

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Message-Id: <20250710005926.1159009-13-ankur.a.arora@oracle.com>
Date: Wed,  9 Jul 2025 17:59:24 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Cc: akpm@...ux-foundation.org, david@...hat.com, 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,
        ankur.a.arora@...cle.com
Subject: [PATCH v5 12/14] mm: add config option for clearing page-extents

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.
+
 # simple helper to make the code a bit easier to read
 config PAGE_MAPCOUNT
 	def_bool !NO_PAGE_MAPCOUNT
-- 
2.43.5