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authorAndrea Arcangeli <aarcange@redhat.com>2011-01-13 15:47:10 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:46 -0800
commit8ee53820edfd1f3b6554c593f337148dd3d7fc91 (patch)
treeca69957e928cd3efa1b47f92dcfb00591702684c /include/linux/mmu_notifier.h
parent4b7167b9ff9b7f3f528cbc4c7d02ebd275b9b10c (diff)
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thp: mmu_notifier_test_young
For GRU and EPT, we need gup-fast to set referenced bit too (this is why it's correct to return 0 when shadow_access_mask is zero, it requires gup-fast to set the referenced bit). qemu-kvm access already sets the young bit in the pte if it isn't zero-copy, if it's zero copy or a shadow paging EPT minor fault we relay on gup-fast to signal the page is in use... We also need to check the young bits on the secondary pagetables for NPT and not nested shadow mmu as the data may never get accessed again by the primary pte. Without this closer accuracy, we'd have to remove the heuristic that avoids collapsing hugepages in hugepage virtual regions that have not even a single subpage in use. ->test_young is full backwards compatible with GRU and other usages that don't have young bits in pagetables set by the hardware and that should nuke the secondary mmu mappings when ->clear_flush_young runs just like EPT does. Removing the heuristic that checks the young bit in khugepaged/collapse_huge_page completely isn't so bad either probably but I thought it was worth it and this makes it reliable. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mmu_notifier.h')
-rw-r--r--include/linux/mmu_notifier.h26
1 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index cbfab1e..cc2e7df 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -62,6 +62,16 @@ struct mmu_notifier_ops {
unsigned long address);
/*
+ * test_young is called to check the young/accessed bitflag in
+ * the secondary pte. This is used to know if the page is
+ * frequently used without actually clearing the flag or tearing
+ * down the secondary mapping on the page.
+ */
+ int (*test_young)(struct mmu_notifier *mn,
+ struct mm_struct *mm,
+ unsigned long address);
+
+ /*
* change_pte is called in cases that pte mapping to page is changed:
* for example, when ksm remaps pte to point to a new shared page.
*/
@@ -163,6 +173,8 @@ extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
extern void __mmu_notifier_release(struct mm_struct *mm);
extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
unsigned long address);
+extern int __mmu_notifier_test_young(struct mm_struct *mm,
+ unsigned long address);
extern void __mmu_notifier_change_pte(struct mm_struct *mm,
unsigned long address, pte_t pte);
extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
@@ -186,6 +198,14 @@ static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
return 0;
}
+static inline int mmu_notifier_test_young(struct mm_struct *mm,
+ unsigned long address)
+{
+ if (mm_has_notifiers(mm))
+ return __mmu_notifier_test_young(mm, address);
+ return 0;
+}
+
static inline void mmu_notifier_change_pte(struct mm_struct *mm,
unsigned long address, pte_t pte)
{
@@ -313,6 +333,12 @@ static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
return 0;
}
+static inline int mmu_notifier_test_young(struct mm_struct *mm,
+ unsigned long address)
+{
+ return 0;
+}
+
static inline void mmu_notifier_change_pte(struct mm_struct *mm,
unsigned long address, pte_t pte)
{
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