From 4645b9fe84bf4878f04c7959a75df7c3c2d1bbb9 Mon Sep 17 00:00:00 2001 From: Jérôme Glisse Date: Wed, 15 Nov 2017 17:34:11 -0800 Subject: mm/mmu_notifier: avoid call to invalidate_range() in range_end() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is an optimization patch that only affect mmu_notifier users which rely on the invalidate_range() callback. This patch avoids calling that callback twice in a row from inside __mmu_notifier_invalidate_range_end Existing pattern (before this patch): mmu_notifier_invalidate_range_start() pte/pmd/pud_clear_flush_notify() mmu_notifier_invalidate_range() mmu_notifier_invalidate_range_end() mmu_notifier_invalidate_range() New pattern (after this patch): mmu_notifier_invalidate_range_start() pte/pmd/pud_clear_flush_notify() mmu_notifier_invalidate_range() mmu_notifier_invalidate_range_only_end() We call the invalidate_range callback after clearing the page table under the page table lock and we skip the call to invalidate_range inside the __mmu_notifier_invalidate_range_end() function. Idea from Andrea Arcangeli Link: http://lkml.kernel.org/r/20171017031003.7481-3-jglisse@redhat.com Signed-off-by: Jérôme Glisse Cc: Andrea Arcangeli Cc: Joerg Roedel Cc: Suravee Suthikulpanit Cc: David Woodhouse Cc: Alistair Popple Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Stephen Rothwell Cc: Andrew Donnellan Cc: Nadav Amit Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'mm/memory.c') diff --git a/mm/memory.c b/mm/memory.c index a4518aedf4dd..42fb30300bb5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2554,7 +2554,11 @@ static int wp_page_copy(struct vm_fault *vmf) put_page(new_page); pte_unmap_unlock(vmf->pte, vmf->ptl); - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + /* + * No need to double call mmu_notifier->invalidate_range() callback as + * the above ptep_clear_flush_notify() did already call it. + */ + mmu_notifier_invalidate_range_only_end(mm, mmun_start, mmun_end); if (old_page) { /* * Don't let another task, with possibly unlocked vma, -- cgit v1.2.3