include/linux/ksm.h

   1 #ifndef __LINUX_KSM_H
   2 #define __LINUX_KSM_H
   3 /*
   4  * Memory merging support.
   5  *
   6  * This code enables dynamic sharing of identical pages found in different
   7  * memory areas, even if they are not shared by fork().
   8  */
   9
  10 #include <linux/bitops.h>
  11 #include <linux/mm.h>
  12 #include <linux/sched.h>
  13 #include <linux/vmstat.h>
  14
  15 struct stable_node;
  16
  17 #ifdef CONFIG_KSM
  18 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  19                 unsigned long end, int advice, unsigned long *vm_flags);
  20 int __ksm_enter(struct mm_struct *mm);
  21 void __ksm_exit(struct mm_struct *mm);
  22
  23 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  24 {
  25         if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  26                 return __ksm_enter(mm);
  27         return 0;
  28 }
  29
  30 static inline void ksm_exit(struct mm_struct *mm)
  31 {
  32         if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  33                 __ksm_exit(mm);
  34 }
  35
  36 /*
  37  * A KSM page is one of those write-protected "shared pages" or "merged pages"
  38  * which KSM maps into multiple mms, wherever identical anonymous page content
  39  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
  40  * anon_vma, but to that page's node of the stable tree.
  41  */
  42 static inline int PageKsm(struct page *page)
  43 {
  44         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
  45                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  46 }
  47
  48 static inline struct stable_node *page_stable_node(struct page *page)
  49 {
  50         return PageKsm(page) ? page_rmapping(page) : NULL;
  51 }
  52
  53 static inline void set_page_stable_node(struct page *page,
  54                                         struct stable_node *stable_node)
  55 {
  56         page->mapping = (void *)stable_node +
  57                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  58 }
  59
  60 static inline void page_add_ksm_rmap(struct page *page)
  61 {
  62         if (atomic_inc_and_test(&page->_mapcount))
  63                 __inc_zone_page_state(page, NR_ANON_PAGES);
  64 }
  65 #else  /* !CONFIG_KSM */
  66
  67 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  68                 unsigned long end, int advice, unsigned long *vm_flags)
  69 {
  70         return 0;
  71 }
  72
  73 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  74 {
  75         return 0;
  76 }
  77
  78 static inline void ksm_exit(struct mm_struct *mm)
  79 {
  80 }
  81
  82 static inline int PageKsm(struct page *page)
  83 {
  84         return 0;
  85 }
  86
  87 /* No stub required for page_add_ksm_rmap(page) */
  88 #endif /* !CONFIG_KSM */
  89
  90 #endif