From 08beca44dfb0ab008e365163df70dbd302ae1508 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 14 Dec 2009 17:59:21 -0800 Subject: 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 Cc: Izik Eidus Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/ksm.h | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) (limited to 'include/linux') 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 #include +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 */ -- cgit v1.2.3