path: root/include/linux/ksm.h
diff options
authorHugh Dickins <hugh.dickins@tiscali.co.uk>2009-09-21 17:02:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:31 -0700
commit9a840895147b12de5cdd633c600b38686840ee53 (patch)
treea266a69a39decb4ec0364ac331f0ab19b6f09f06 /include/linux/ksm.h
parent21333b2b66b805a360641568588e5a0bb06d9d1f (diff)
ksm: identify PageKsm pages
KSM will need to identify its kernel merged pages unambiguously, and /proc/kpageflags will probably like to do so too. Since KSM will only be substituting anonymous pages, statistics are best preserved by making a PageKsm page a special PageAnon page: one with no anon_vma. But KSM then needs its own page_add_ksm_rmap() - keep it in ksm.h near PageKsm; and do_wp_page() must COW them, unlike singly mapped PageAnons. Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by: Chris Wright <chrisw@redhat.com> Signed-off-by: Izik Eidus <ieidus@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Avi Kivity <avi@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/ksm.h')
1 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index eb2a448981ee..a485c14ecd5d 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -10,6 +10,7 @@
#include <linux/bitops.h>
#include <linux/mm.h>
#include <linux/sched.h>
+#include <linux/vmstat.h>
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -29,6 +30,27 @@ static inline void ksm_exit(struct mm_struct *mm)
if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+ * 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.
+ */
+static inline int PageKsm(struct page *page)
+ return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
+ * But we have to avoid the checking which page_add_anon_rmap() performs.
+ */
+static inline void page_add_ksm_rmap(struct page *page)
+ if (atomic_inc_and_test(&page->_mapcount)) {
+ page->mapping = (void *) PAGE_MAPPING_ANON;
+ __inc_zone_page_state(page, NR_ANON_PAGES);
+ }
#else /* !CONFIG_KSM */
static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -45,6 +67,13 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
static inline void ksm_exit(struct mm_struct *mm)
+static inline int PageKsm(struct page *page)
+ return 0;
+/* No stub required for page_add_ksm_rmap(page) */
#endif /* !CONFIG_KSM */