diff options
| author | Hugh Dickins <hugh.dickins@tiscali.co.uk> | 2009-12-14 17:59:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-15 08:53:19 -0800 |
| commit | 08beca44dfb0ab008e365163df70dbd302ae1508 (patch) | |
| tree | 33f3ddf5460e139bd7fd37e8c08026a7d852c3da /include | |
| parent | 7b6ba2c7d3baf8cd9f888e05563dcc32e368baab (diff) | |
ksm: stable_node point to page and back
Add a pointer to the ksm page into struct stable_node, holding a reference
to the page while the node exists. Put a pointer to the stable_node into
the ksm page's ->mapping.
Then we don't need get_ksm_page() while traversing the stable tree: the
page to compare against is sure to be present and correct, even if it's no
longer visible through any of its existing rmap_items.
And we can handle the forked ksm page case more efficiently: no need to
memcmp our way through the tree to find its match.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: 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')
| -rw-r--r-- | include/linux/ksm.h | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 1401a313fa77..ef55ce14a2ce 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -12,6 +12,8 @@ #include <linux/sched.h> #include <linux/vmstat.h> +struct stable_node; + #ifdef CONFIG_KSM int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags); @@ -34,7 +36,8 @@ static inline void ksm_exit(struct mm_struct *mm) /* * A KSM page is one of those write-protected "shared pages" or "merged pages" * which KSM maps into multiple mms, wherever identical anonymous page content - * is found in VM_MERGEABLE vmas. It's a PageAnon page, with NULL anon_vma. + * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any + * anon_vma, but to that page's node of the stable tree. */ static inline int PageKsm(struct page *page) { @@ -42,15 +45,22 @@ static inline int PageKsm(struct page *page) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); } -/* - * But we have to avoid the checking which page_add_anon_rmap() performs. - */ +static inline struct stable_node *page_stable_node(struct page *page) +{ + return PageKsm(page) ? page_rmapping(page) : NULL; +} + +static inline void set_page_stable_node(struct page *page, + struct stable_node *stable_node) +{ + page->mapping = (void *)stable_node + + (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); +} + static inline void page_add_ksm_rmap(struct page *page) { - if (atomic_inc_and_test(&page->_mapcount)) { - page->mapping = (void *) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); + if (atomic_inc_and_test(&page->_mapcount)) __inc_zone_page_state(page, NR_ANON_PAGES); - } } #else /* !CONFIG_KSM */ |