From e178dfde3952192cf44eeb0612882f01fc96c0a9 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 21 Sep 2009 17:02:10 -0700 Subject: [PATCH] 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 Acked-by: Izik Eidus Acked-by: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/ksm.c | 24 +++++++++--------------- 1 file changed, 9 insertions(+), 15 deletions(-) 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 @@ 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); -- 2.7.4