The quilt patch titled
Subject: mm: CONFIG_NO_PAGE_MAPCOUNT to prepare for not maintain per-page mapcounts in large folios
has been removed from the -mm tree. Its filename was
mm-config_no_page_mapcount-to-prepare-for-not-maintain-per-page-mapcounts-in-large-folios.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm: CONFIG_NO_PAGE_MAPCOUNT to prepare for not maintain per-page mapcounts in large folios
Date: Mon, 3 Mar 2025 17:30:08 +0100
We're close to the finishing line: let's introduce a new
CONFIG_NO_PAGE_MAPCOUNT config option where we will incrementally remove
any dependencies on per-page mapcounts in large folios. Once that's done,
we'll stop maintaining the per-page mapcounts with this config option
enabled.
CONFIG_NO_PAGE_MAPCOUNT will be EXPERIMENTAL for now, as we'll have to
learn about some of the real world impact of some of the implications.
As writing "!CONFIG_NO_PAGE_MAPCOUNT" is really nasty, let's introduce a
helper config option "CONFIG_PAGE_MAPCOUNT" that expresses the negation.
Link: https://lkml.kernel.org/r/20250303163014.1128035-16-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andy Lutomirks^H^Hski <luto@xxxxxxxxxx>
Cc: Borislav Betkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lance Yang <ioworker0@xxxxxxxxx>
Cc: Liam Howlett <liam.howlett@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Matthew Wilcow (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michal Koutn <mkoutny@xxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: tejun heo <tj@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Zefan Li <lizefan.x@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/Kconfig | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
--- a/mm/Kconfig~mm-config_no_page_mapcount-to-prepare-for-not-maintain-per-page-mapcounts-in-large-folios
+++ a/mm/Kconfig
@@ -887,8 +887,25 @@ config READ_ONLY_THP_FOR_FS
support of file THPs will be developed in the next few release
cycles.
+config NO_PAGE_MAPCOUNT
+ bool "No per-page mapcount (EXPERIMENTAL)"
+ help
+ Do not maintain per-page mapcounts for pages part of larger
+ allocations, such as transparent huge pages.
+
+ When this config option is enabled, some interfaces that relied on
+ this information will rely on less-precise per-allocation information
+ instead: for example, using the average per-page mapcount in such
+ a large allocation instead of the per-page mapcount.
+
+ EXPERIMENTAL because the impact of some changes is still unclear.
+
endif # TRANSPARENT_HUGEPAGE
+# simple helper to make the code a bit easier to read
+config PAGE_MAPCOUNT
+ def_bool !NO_PAGE_MAPCOUNT
+
#
# The architecture supports pgtable leaves that is larger than PAGE_SIZE
#
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
