has_fast_aging should be set by subscribers that non-trivially implement fast_only versions of both test_young() and clear_young(). Fast aging must be opt-in. For a subscriber that has not been enlightened with "fast aging", the test/clear_young() will behave identically whether or not fast_only is given. Given that KVM is the only test/clear_young() implementer, we could instead add an equivalent check in KVM, but doing so would incur an indirect function call every time, even if the notifier ends up being a no-op. Add mm_has_fast_young_notifiers() in case a caller wants to know if it should skip many calls to the mmu notifiers that may not be necessary (like MGLRU look-around). Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx> --- include/linux/mmu_notifier.h | 14 ++++++++++++++ mm/mmu_notifier.c | 26 ++++++++++++++++++++++++++ 2 files changed, 40 insertions(+) diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index 45c5995ebd84..e23fc10f864b 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -233,6 +233,7 @@ struct mmu_notifier { struct mm_struct *mm; struct rcu_head rcu; unsigned int users; + bool has_fast_aging; }; /** @@ -387,6 +388,7 @@ extern int __mmu_notifier_clear_young(struct mm_struct *mm, extern int __mmu_notifier_test_young(struct mm_struct *mm, unsigned long address, bool fast_only); +extern bool __mm_has_fast_young_notifiers(struct mm_struct *mm); extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r); extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r); extern void __mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm, @@ -449,6 +451,13 @@ static inline int mmu_notifier_test_young_fast_only(struct mm_struct *mm, return 0; } +static inline bool mm_has_fast_young_notifiers(struct mm_struct *mm) +{ + if (mm_has_notifiers(mm)) + return __mm_has_fast_young_notifiers(mm); + return 0; +} + static inline void mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) { @@ -653,6 +662,11 @@ static inline int mmu_notifier_test_young_fast_only(struct mm_struct *mm, return 0; } +static inline bool mm_has_fast_young_notifiers(struct mm_struct *mm) +{ + return 0; +} + static inline void mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) { diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index f9a0ca6ffe65..f9ec810c8a1b 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -382,6 +382,26 @@ int __mmu_notifier_clear_flush_young(struct mm_struct *mm, return young; } +bool __mm_has_fast_young_notifiers(struct mm_struct *mm) +{ + struct mmu_notifier *subscription; + bool has_fast_aging = false; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(subscription, + &mm->notifier_subscriptions->list, hlist, + srcu_read_lock_held(&srcu)) { + if (subscription->has_fast_aging) { + has_fast_aging = true; + break; + } + } + srcu_read_unlock(&srcu, id); + + return has_fast_aging; +} + int __mmu_notifier_clear_young(struct mm_struct *mm, unsigned long start, unsigned long end, @@ -394,6 +414,9 @@ int __mmu_notifier_clear_young(struct mm_struct *mm, hlist_for_each_entry_rcu(subscription, &mm->notifier_subscriptions->list, hlist, srcu_read_lock_held(&srcu)) { + if (fast_only && !subscription->has_fast_aging) + continue; + if (subscription->ops->clear_young) young |= subscription->ops->clear_young(subscription, mm, start, end, @@ -415,6 +438,9 @@ int __mmu_notifier_test_young(struct mm_struct *mm, hlist_for_each_entry_rcu(subscription, &mm->notifier_subscriptions->list, hlist, srcu_read_lock_held(&srcu)) { + if (fast_only && !subscription->has_fast_aging) + continue; + if (subscription->ops->test_young) { young = subscription->ops->test_young(subscription, mm, address, -- 2.46.0.rc1.232.g9752f9e123-goog