diff options
| author | David Hildenbrand <david@redhat.com> | 2025-03-03 17:30:08 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-03-17 22:06:46 -0700 |
| commit | e63ee43e3edaacfca04454b34aee8d5e303953df (patch) | |
| tree | 05900329f036ea7040d9947594286a7767f65cbf /mm | |
| parent | 003fde4492c88ac3a1fee3d97b3834a679780af3 (diff) | |
mm: CONFIG_NO_PAGE_MAPCOUNT to prepare for not maintain per-page mapcounts in large folios
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@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirks^H^Hski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michal Koutn <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: tejun heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/Kconfig | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index a25c5476b3ad4..4a4e7b63d30a8 100644 --- a/mm/Kconfig +++ b/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 # |