The patch titled
Subject: mm: migrate: do not migrate HugeTLB page whose refcount is one
has been added to the -mm tree. Its filename is
mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: migrate: do not migrate HugeTLB page whose refcount is one
If the refcount is one when it is migrated, it means that the page
was freed from under us. So we are done and do not need to migrate.
This optimization is consistent with the regular pages, just like
unmap_and_move() does.
Link: https://lkml.kernel.org/r/20210110124017.86750-2-songmuchun@xxxxxxxxxxxxx
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/mm/migrate.c~mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one
+++ a/mm/migrate.c
@@ -1284,6 +1284,12 @@ static int unmap_and_move_huge_page(new_
return -ENOSYS;
}
+ if (page_count(hpage) == 1) {
+ /* page was freed from under us. So we are done. */
+ putback_active_hugepage(hpage);
+ return MIGRATEPAGE_SUCCESS;
+ }
+
new_hpage = get_new_page(hpage, private);
if (!new_hpage)
return -ENOMEM;
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-hugetlbfs-fix-cannot-migrate-the-fallocated-hugetlb-page.patch
mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch
mm-hugetlb-fix-a-race-between-isolating-and-freeing-page.patch
mm-hugetlb-remove-vm_bug_on_page-from-page_huge_active.patch
mm-memcontrol-optimize-per-lruvec-stats-counter-memory-usage.patch
mm-memcontrol-fix-nr_anon_thps-accounting-in-charge-moving.patch
mm-memcontrol-convert-nr_anon_thps-account-to-pages.patch
mm-memcontrol-convert-nr_file_thps-account-to-pages.patch
mm-memcontrol-convert-nr_shmem_thps-account-to-pages.patch
mm-memcontrol-convert-nr_shmem_pmdmapped-account-to-pages.patch
mm-memcontrol-convert-nr_file_pmdmapped-account-to-pages.patch
mm-memcontrol-make-the-slab-calculation-consistent.patch
mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
mm-hugetlb-add-return-eagain-for-dissolve_free_huge_page.patch
