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 #ifdef CONFIG_KSM
  16 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  17                 unsigned long end, int advice, unsigned long *vm_flags);
  18 int __ksm_enter(struct mm_struct *mm);
  19 void __ksm_exit(struct mm_struct *mm);
  20
  21 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  22 {
  23         if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  24                 return __ksm_enter(mm);
  25         return 0;
  26 }
  27
  28 static inline void ksm_exit(struct mm_struct *mm)
  29 {
  30         if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  31                 __ksm_exit(mm);
  32 }
  33
  34 /*
  35  * A KSM page is one of those write-protected "shared pages" or "merged pages"
  36  * which KSM maps into multiple mms, wherever identical anonymous page content
  37  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, with NULL anon_vma.
  38  */
  39 static inline int PageKsm(struct page *page)
  40 {
  41         return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
  42 }
  43
  44 /*
  45  * But we have to avoid the checking which page_add_anon_rmap() performs.
  46  */
  47 static inline void page_add_ksm_rmap(struct page *page)
  48 {
  49         if (atomic_inc_and_test(&page->_mapcount)) {
  50                 page->mapping = (void *) PAGE_MAPPING_ANON;
  51                 __inc_zone_page_state(page, NR_ANON_PAGES);
  52         }
  53 }
  54 #else  /* !CONFIG_KSM */
  55
  56 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  57                 unsigned long end, int advice, unsigned long *vm_flags)
  58 {
  59         return 0;
  60 }
  61
  62 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  63 {
  64         return 0;
  65 }
  66
  67 static inline void ksm_exit(struct mm_struct *mm)
  68 {
  69 }
  70
  71 static inline int PageKsm(struct page *page)
  72 {
  73         return 0;
  74 }
  75
  76 /* No stub required for page_add_ksm_rmap(page) */
  77 #endif /* !CONFIG_KSM */
  78
  79 #endif