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Commit 4645b9fe authored by Jérôme Glisse's avatar Jérôme Glisse Committed by Linus Torvalds
Browse files

mm/mmu_notifier: avoid call to invalidate_range() in range_end() 

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: default avatarJérôme Glisse <jglisse@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alistair Popple <alistair@popple.id.au>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0f10851e

include/linux/mmu_notifier.h

+15 −2
Original line number Diff line number Diff line
@@ -214,7 +214,8 @@ extern void __mmu_notifier_change_pte(struct mm_struct *mm, 
extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,

				  unsigned long start, unsigned long end);

extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,

				  unsigned long start, unsigned long end);

				  unsigned long start, unsigned long end,

				  bool only_end);

extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,

				  unsigned long start, unsigned long end);
@@ -268,7 +269,14 @@ static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, 
				  unsigned long start, unsigned long end)

{

	if (mm_has_notifiers(mm))

		__mmu_notifier_invalidate_range_end(mm, start, end);

		__mmu_notifier_invalidate_range_end(mm, start, end, false);

}



static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm,

				  unsigned long start, unsigned long end)

{

	if (mm_has_notifiers(mm))

		__mmu_notifier_invalidate_range_end(mm, start, end, true);

}



static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
@@ -439,6 +447,11 @@ static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, 
{

}



static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm,

				  unsigned long start, unsigned long end)

{

}



static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,

				  unsigned long start, unsigned long end)

{

mm/huge_memory.c

+42 −4
Original line number Diff line number Diff line
@@ -1223,7 +1223,12 @@ static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd, 
	page_remove_rmap(page, true);

	spin_unlock(vmf->ptl);



	mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);

	/*

	 * No need to double call mmu_notifier->invalidate_range() callback as

	 * the above pmdp_huge_clear_flush_notify() did already call it.

	 */

	mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,

						mmun_end);



	ret |= VM_FAULT_WRITE;

	put_page(page);
@@ -1372,7 +1377,12 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) 
	}

	spin_unlock(vmf->ptl);

out_mn:

	mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);

	/*

	 * No need to double call mmu_notifier->invalidate_range() callback as

	 * the above pmdp_huge_clear_flush_notify() did already call it.

	 */

	mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,

					       mmun_end);

out:

	return ret;

out_unlock:
@@ -2024,7 +2034,12 @@ void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, 


out:

	spin_unlock(ptl);

	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PUD_SIZE);

	/*

	 * No need to double call mmu_notifier->invalidate_range() callback as

	 * the above pudp_huge_clear_flush_notify() did already call it.

	 */

	mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +

					       HPAGE_PUD_SIZE);

}

#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
@@ -2099,6 +2114,15 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
		add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);

		return;

	} else if (is_huge_zero_pmd(*pmd)) {

		/*

		 * FIXME: Do we want to invalidate secondary mmu by calling

		 * mmu_notifier_invalidate_range() see comments below inside

		 * __split_huge_pmd() ?

		 *

		 * We are going from a zero huge page write protected to zero

		 * small page also write protected so it does not seems useful

		 * to invalidate secondary mmu at this time.

		 */

		return __split_huge_zero_page_pmd(vma, haddr, pmd);

	}
@@ -2234,7 +2258,21 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 
	__split_huge_pmd_locked(vma, pmd, haddr, freeze);

out:

	spin_unlock(ptl);

	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);

	/*

	 * No need to double call mmu_notifier->invalidate_range() callback.

	 * They are 3 cases to consider inside __split_huge_pmd_locked():

	 *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious

	 *  2) __split_huge_zero_page_pmd() read only zero page and any write

	 *    fault will trigger a flush_notify before pointing to a new page

	 *    (it is fine if the secondary mmu keeps pointing to the old zero

	 *    page in the meantime)

	 *  3) Split a huge pmd into pte pointing to the same page. No need

	 *     to invalidate secondary tlb entry they are all still valid.

	 *     any further changes to individual pte will notify. So no need

	 *     to call mmu_notifier->invalidate_range()

	 */

	mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +

					       HPAGE_PMD_SIZE);

}



void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,

mm/memory.c

+5 −1
Original line number Diff line number Diff line
@@ -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,

mm/migrate.c

+12 −3
Original line number Diff line number Diff line
@@ -2089,7 +2089,11 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, 
	set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);



	spin_unlock(ptl);

	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);

	/*

	 * No need to double call mmu_notifier->invalidate_range() callback as

	 * the above pmdp_huge_clear_flush_notify() did already call it.

	 */

	mmu_notifier_invalidate_range_only_end(mm, mmun_start, mmun_end);



	/* Take an "isolate" reference and put new page on the LRU. */

	get_page(new_page);
@@ -2805,8 +2809,13 @@ static void migrate_vma_pages(struct migrate_vma *migrate) 
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;

	}



	/*

	 * No need to double call mmu_notifier->invalidate_range() callback as

	 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()

	 * did already call it.

	 */

	if (notified)

		mmu_notifier_invalidate_range_end(mm, mmu_start,

		mmu_notifier_invalidate_range_only_end(mm, mmu_start,

						       migrate->end);

}

mm/mmu_notifier.c

+9 −2
Original line number Diff line number Diff line
@@ -190,7 +190,9 @@ void __mmu_notifier_invalidate_range_start(struct mm_struct *mm, 
EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);



void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,

				  unsigned long start, unsigned long end)

					 unsigned long start,

					 unsigned long end,

					 bool only_end)

{

	struct mmu_notifier *mn;

	int id;
@@ -204,8 +206,13 @@ void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, 
		 * subsystem registers either invalidate_range_start()/end() or

		 * invalidate_range(), so this will be no additional overhead

		 * (besides the pointer check).

		 *

		 * We skip call to invalidate_range() if we know it is safe ie

		 * call site use mmu_notifier_invalidate_range_only_end() which

		 * is safe to do when we know that a call to invalidate_range()

		 * already happen under page table lock.

		 */

		if (mn->ops->invalidate_range)

		if (!only_end && mn->ops->invalidate_range)

			mn->ops->invalidate_range(mn, mm, start, end);

		if (mn->ops->invalidate_range_end)

			mn->ops->invalidate_range_end(mn, mm, start, end);