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ksm: move pages_sharing updates 

The pages_shared count is incremented and decremented when adding a node
to and removing a node from the stable tree: easy to understand.  But the
pages_sharing count was hard to follow, being adjusted in various places:
increment and decrement it when adding to and removing from the stable tree.

And the pages_sharing variable used to include the pages_shared, then those
were subtracted when shown in the pages_sharing sysfs file: now keep it as
an exclusive count of leaves hanging off the stable tree nodes, throughout.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Izik Eidus <ieidus@redhat.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2009-09-21 17:02:10 -07:00 committed by Linus Torvalds
parent b402826033
commit e178dfde39
1 changed files with 9 additions and 15 deletions
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24
mm/ksm.c
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@ -152,7 +152,7 @@ static struct kmem_cache *mm_slot_cache;
/* The number of nodes in the stable tree */
static unsigned long ksm_pages_shared;
/* The number of page slots sharing those nodes */
/* The number of page slots additionally sharing those nodes */
static unsigned long ksm_pages_sharing;
/* Limit on the number of unswappable pages used */
@ -382,6 +382,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
&next_item->node,
&root_stable_tree);
next_item->address |= NODE_FLAG;
ksm_pages_sharing--;
} else {
rb_erase(&rmap_item->node, &root_stable_tree);
ksm_pages_shared--;
@ -395,10 +396,10 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
BUG_ON(next_item->prev != rmap_item);
next_item->prev = rmap_item->prev;
}
ksm_pages_sharing--;
}
rmap_item->next = NULL;
ksm_pages_sharing--;
} else if (rmap_item->address & NODE_FLAG) {
unsigned char age;
@ -786,8 +787,6 @@ static int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1,
*/
if (err)
break_cow(mm1, addr1);
else
ksm_pages_sharing += 2;
}
put_page(kpage);
@ -816,9 +815,6 @@ static int try_to_merge_with_ksm_page(struct mm_struct *mm1,
err = try_to_merge_one_page(vma, page1, kpage);
up_read(&mm1->mmap_sem);
if (!err)
ksm_pages_sharing++;
return err;
}
@ -928,13 +924,12 @@ static struct rmap_item *stable_tree_insert(struct page *page,
}
}
ksm_pages_shared++;
rmap_item->address |= NODE_FLAG | STABLE_FLAG;
rmap_item->next = NULL;
rb_link_node(&rmap_item->node, parent, new);
rb_insert_color(&rmap_item->node, &root_stable_tree);
ksm_pages_shared++;
return rmap_item;
}
@ -1019,6 +1014,8 @@ static void stable_tree_append(struct rmap_item *rmap_item,
tree_rmap_item->next = rmap_item;
rmap_item->address |= STABLE_FLAG;
ksm_pages_sharing++;
}
/*
@ -1043,10 +1040,9 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
/* We first start with searching the page inside the stable tree */
tree_rmap_item = stable_tree_search(page, page2, rmap_item);
if (tree_rmap_item) {
if (page == page2[0]) { /* forked */
ksm_pages_sharing++;
if (page == page2[0]) /* forked */
err = 0;
} else
else
err = try_to_merge_with_ksm_page(rmap_item->mm,
rmap_item->address,
page, page2[0]);
@ -1107,7 +1103,6 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
break_cow(tree_rmap_item->mm,
tree_rmap_item->address);
break_cow(rmap_item->mm, rmap_item->address);
ksm_pages_sharing -= 2;
}
}
@ -1475,8 +1470,7 @@ KSM_ATTR_RO(pages_shared);
static ssize_t pages_sharing_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%lu\n",
ksm_pages_sharing - ksm_pages_shared);
return sprintf(buf, "%lu\n", ksm_pages_sharing);
}
KSM_ATTR_RO(pages_sharing);