The patch titled
Subject: mm: page_alloc: fix up block types when merging compatible blocks
has been added to the -mm mm-unstable branch. Its filename is
mm-page_alloc-fix-up-block-types-when-merging-compatible-blocks.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-fix-up-block-types-when-merging-compatible-blocks.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: page_alloc: fix up block types when merging compatible blocks
Date: Wed, 20 Mar 2024 14:02:08 -0400
The buddy allocator coalesces compatible blocks during freeing, but it
doesn't update the types of the subblocks to match. When an allocation
later breaks the chunk down again, its pieces will be put on freelists of
the wrong type. This encourages incompatible page mixing (ask for one
type, get another), and thus long-term fragmentation.
Update the subblocks when merging a larger chunk, such that a later
expand() will maintain freelist type hygiene.
Link: https://lkml.kernel.org/r/20240320180429.678181-4-hannes@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Tested-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-fix-up-block-types-when-merging-compatible-blocks
+++ a/mm/page_alloc.c
@@ -786,10 +786,17 @@ static inline void __free_one_page(struc
*/
int buddy_mt = get_pfnblock_migratetype(buddy, buddy_pfn);
- if (migratetype != buddy_mt
- && (!migratetype_is_mergeable(migratetype) ||
- !migratetype_is_mergeable(buddy_mt)))
- goto done_merging;
+ if (migratetype != buddy_mt) {
+ if (!migratetype_is_mergeable(migratetype) ||
+ !migratetype_is_mergeable(buddy_mt))
+ goto done_merging;
+ /*
+ * Match buddy type. This ensures that
+ * an expand() down the line puts the
+ * sub-blocks on the right freelists.
+ */
+ set_pageblock_migratetype(buddy, migratetype);
+ }
}
/*
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
mm-cachestat-fix-two-shmem-bugs.patch
mm-zswap-fix-writeback-shinker-gfp_noio-gfp_nofs-recursion.patch
mm-zswap-optimize-zswap-pool-size-tracking.patch
mm-zpool-return-pool-size-in-pages.patch
mm-page_alloc-remove-pcppage-migratetype-caching.patch
mm-page_alloc-optimize-free_unref_folios.patch
mm-page_alloc-fix-up-block-types-when-merging-compatible-blocks.patch
mm-page_alloc-move-free-pages-when-converting-block-during-isolation.patch
mm-page_alloc-fix-move_freepages_block-range-error.patch
mm-page_alloc-fix-freelist-movement-during-block-conversion.patch
mm-page_alloc-close-migratetype-race-between-freeing-and-stealing.patch
mm-page_isolation-prepare-for-hygienic-freelists.patch
mm-page_isolation-prepare-for-hygienic-freelists-fix.patch
mm-page_alloc-consolidate-free-page-accounting.patch
