LXR linux/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
  16int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  17                unsigned long end, int advice, unsigned long *vm_flags);
  18int __ksm_enter(struct mm_struct *mm);
  19void __ksm_exit(struct mm_struct *mm);
  20
  21static 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
  28static 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 */
  39static 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 */
  47static 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
  56static 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
  62static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  63{
  64        return 0;
  65}
  66
  67static inline void ksm_exit(struct mm_struct *mm)
  68{
  69}
  70
  71static 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
  80