From 1d7715c676a1566c2e4c3e77d16b1f9bb4909025 Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Wed, 9 Sep 2015 15:35:41 -0700 Subject: mmu-notifier: add clear_young callback In the scope of the idle memory tracking feature, which is introduced by the following patch, we need to clear the referenced/accessed bit not only in primary, but also in secondary ptes. The latter is required in order to estimate wss of KVM VMs. At the same time we want to avoid flushing tlb, because it is quite expensive and it won't really affect the final result. Currently, there is no function for clearing pte young bit that would meet our requirements, so this patch introduces one. To achieve that we have to add a new mmu-notifier callback, clear_young, since there is no method for testing-and-clearing a secondary pte w/o flushing tlb. The new method is not mandatory and currently only implemented by KVM. Signed-off-by: Vladimir Davydov Reviewed-by: Andres Lagar-Cavilla Acked-by: Paolo Bonzini Cc: Minchan Kim Cc: Raghavendra K T Cc: Johannes Weiner Cc: Michal Hocko Cc: Greg Thelen Cc: Michel Lespinasse Cc: David Rientjes Cc: Pavel Emelyanov Cc: Cyrill Gorcunov Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmu_notifier.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) (limited to 'include') diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index 61cd67f4d788..a5b17137c683 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -65,6 +65,16 @@ struct mmu_notifier_ops { unsigned long start, unsigned long end); + /* + * clear_young is a lightweight version of clear_flush_young. Like the + * latter, it is supposed to test-and-clear the young/accessed bitflag + * in the secondary pte, but it may omit flushing the secondary tlb. + */ + int (*clear_young)(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long start, + unsigned long end); + /* * test_young is called to check the young/accessed bitflag in * the secondary pte. This is used to know if the page is @@ -203,6 +213,9 @@ extern void __mmu_notifier_release(struct mm_struct *mm); extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm, unsigned long start, unsigned long end); +extern int __mmu_notifier_clear_young(struct mm_struct *mm, + unsigned long start, + unsigned long end); extern int __mmu_notifier_test_young(struct mm_struct *mm, unsigned long address); extern void __mmu_notifier_change_pte(struct mm_struct *mm, @@ -231,6 +244,15 @@ static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm, return 0; } +static inline int mmu_notifier_clear_young(struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + if (mm_has_notifiers(mm)) + return __mmu_notifier_clear_young(mm, start, end); + return 0; +} + static inline int mmu_notifier_test_young(struct mm_struct *mm, unsigned long address) { @@ -311,6 +333,28 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) __young; \ }) +#define ptep_clear_young_notify(__vma, __address, __ptep) \ +({ \ + int __young; \ + struct vm_area_struct *___vma = __vma; \ + unsigned long ___address = __address; \ + __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\ + __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \ + ___address + PAGE_SIZE); \ + __young; \ +}) + +#define pmdp_clear_young_notify(__vma, __address, __pmdp) \ +({ \ + int __young; \ + struct vm_area_struct *___vma = __vma; \ + unsigned long ___address = __address; \ + __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\ + __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \ + ___address + PMD_SIZE); \ + __young; \ +}) + #define ptep_clear_flush_notify(__vma, __address, __ptep) \ ({ \ unsigned long ___addr = __address & PAGE_MASK; \ -- cgit v1.2.3