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| author | Yu Zhao <yuzhao@google.com> | 2024-09-05 22:21:07 -0600 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-09-09 16:39:18 -0700 |
| commit | 95599ef684d01136a8b77c16a7c853496786e173 (patch) | |
| tree | cbaef339de8dbf2badd38ba8c05a80532b3172e6 /mm/huge_memory.c | |
| parent | eebc0f48468e68b93393d11f75ad17385a9acca8 (diff) | |
| download | linux-95599ef684d01136a8b77c16a7c853496786e173.tar.gz linux-95599ef684d01136a8b77c16a7c853496786e173.tar.bz2 linux-95599ef684d01136a8b77c16a7c853496786e173.zip | |
mm/codetag: fix pgalloc_tag_split()
The current assumption is that a large folio can only be split into
order-0 folios. That is not the case for hugeTLB demotion, nor for THP
split: see commit c010d47f107f ("mm: thp: split huge page to any lower
order pages").
When a large folio is split into ones of a lower non-zero order, only the
new head pages should be tagged. Tagging tail pages can cause imbalanced
"calls" counters, since only head pages are untagged by pgalloc_tag_sub()
and the "calls" counts on tail pages are leaked, e.g.,
# echo 2048kB >/sys/kernel/mm/hugepages/hugepages-1048576kB/demote_size
# echo 700 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
# time echo 700 >/sys/kernel/mm/hugepages/hugepages-1048576kB/demote
# echo 0 >/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
# grep alloc_gigantic_folio /proc/allocinfo
Before this patch:
0 549427200 mm/hugetlb.c:1549 func:alloc_gigantic_folio
real 0m2.057s
user 0m0.000s
sys 0m2.051s
After this patch:
0 0 mm/hugetlb.c:1549 func:alloc_gigantic_folio
real 0m1.711s
user 0m0.000s
sys 0m1.704s
Not tagging tail pages also improves the splitting time, e.g., by about
15% when demoting 1GB hugeTLB folios to 2MB ones, as shown above.
Link: https://lkml.kernel.org/r/20240906042108.1150526-2-yuzhao@google.com
Fixes: be25d1d4e822 ("mm: create new codetag references during page splitting")
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f15f7faf2a63..cc2872f12030 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3226,7 +3226,7 @@ static void __split_huge_page(struct page *page, struct list_head *list, /* Caller disabled irqs, so they are still disabled here */ split_page_owner(head, order, new_order); - pgalloc_tag_split(head, 1 << order); + pgalloc_tag_split(folio, order, new_order); /* See comment in __split_huge_page_tail() */ if (folio_test_anon(folio)) { |