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>
diff --git a/mm/ksm.c b/mm/ksm.c
index 46b4c52..ef89526 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -152,7 +152,7 @@
/* 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 @@
&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 @@
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 @@
*/
if (err)
break_cow(mm1, addr1);
- else
- ksm_pages_sharing += 2;
}
put_page(kpage);
@@ -816,9 +815,6 @@
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 @@
}
}
- 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 @@
tree_rmap_item->next = rmap_item;
rmap_item->address |= STABLE_FLAG;
+
+ ksm_pages_sharing++;
}
/*
@@ -1043,10 +1040,9 @@
/* 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 @@
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 @@
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);