Commit 67e4eb07 authored Jun 03, 2020 by Yang Shi Committed by Linus Torvalds Jun 03, 2020

mm: thp: don't need to drain lru cache when splitting and mlocking THP



Since commit 8f182270 ("mm/swap.c: flush lru pvecs on compound page
arrival") THP would not stay in pagevec anymore.  So the optimization made
by commit d9654322 ("thp: increase split_huge_page() success rate")
doesn't make sense anymore, which tries to unpin munlocked THPs from
pagevec by draining pagevec.

Draining lru cache before isolating THP in mlock path is also unnecessary.
b676b293 ("mm, thp: fix mapped pages avoiding unevictable list on
mlock") added it and 9a73f61b ("thp, mlock: do not mlock PTE-mapped
file huge pages") accidentally carried it over after the above
optimization went in.

Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Link: http://lkml.kernel.org/r/1585946493-7531-1-git-send-email-yang.shi@linux.alibaba.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 88590253

mm/huge_memory.c

+0 −7

Original line number	Diff line number	Diff line
		@@ -1378,7 +1378,6 @@ struct page follow_trans_huge_pmd(struct vm_area_struct vma,
		goto skip_mlock;
		if (!trylock_page(page))
		goto skip_mlock;
		lru_add_drain();
		if (page->mapping && !PageDoubleMap(page))
		mlock_vma_page(page);
		unlock_page(page);
		@@ -2582,7 +2581,6 @@ int split_huge_page_to_list(struct page page, struct list_head list)
		struct anon_vma *anon_vma = NULL;
		struct address_space *mapping = NULL;
		int count, mapcount, extra_pins, ret;
		bool mlocked;
		unsigned long flags;
		pgoff_t end;

		@@ -2641,14 +2639,9 @@ int split_huge_page_to_list(struct page page, struct list_head list)
		goto out_unlock;
		}

		mlocked = PageMlocked(head);
		unmap_page(head);
		VM_BUG_ON_PAGE(compound_mapcount(head), head);

		/* Make sure the page is not on per-CPU pagevec as it takes pin */
		if (mlocked)
		lru_add_drain();

		/* prevent PageLRU to go away from under us, and freeze lru stats */
		spin_lock_irqsave(&pgdata->lru_lock, flags);

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