From 473b0ce4d13ee77925a7062e25dea0d16a91f654 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 21 Sep 2009 17:02:11 -0700 Subject: [PATCH] ksm: pages_unshared and pages_volatile The pages_shared and pages_sharing counts give a good picture of how successful KSM is at sharing; but no clue to how much wasted work it's doing to get there. Add pages_unshared (count of unique pages waiting in the unstable tree, hoping to find a mate) and pages_volatile. pages_volatile is harder to define. It includes those pages changing too fast to get into the unstable tree, but also whatever other edge conditions prevent a page getting into the trees: a high value may deserve investigation. Don't try to calculate it from the various conditions: it's the total of rmap_items less those accounted for. Also show full_scans: the number of completed scans of everything registered in the mm list. The locking for all these counts is simply ksm_thread_mutex. 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 | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 51 insertions(+), 1 deletion(-) diff --git a/mm/ksm.c b/mm/ksm.c index ef89526fb862..9f8f0523562b 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -155,6 +155,12 @@ static unsigned long ksm_pages_shared; /* The number of page slots additionally sharing those nodes */ static unsigned long ksm_pages_sharing; +/* The number of nodes in the unstable tree */ +static unsigned long ksm_pages_unshared; + +/* The number of rmap_items in use: to calculate pages_volatile */ +static unsigned long ksm_rmap_items; + /* Limit on the number of unswappable pages used */ static unsigned long ksm_max_kernel_pages; @@ -204,11 +210,17 @@ static void __init ksm_slab_free(void) static inline struct rmap_item *alloc_rmap_item(void) { - return kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); + struct rmap_item *rmap_item; + + rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); + if (rmap_item) + ksm_rmap_items++; + return rmap_item; } static inline void free_rmap_item(struct rmap_item *rmap_item) { + ksm_rmap_items--; rmap_item->mm = NULL; /* debug safety */ kmem_cache_free(rmap_item_cache, rmap_item); } @@ -419,6 +431,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) BUG_ON(age > 2); if (!age) rb_erase(&rmap_item->node, &root_unstable_tree); + ksm_pages_unshared--; } rmap_item->address &= PAGE_MASK; @@ -995,6 +1008,7 @@ static struct rmap_item *unstable_tree_search_insert(struct page *page, rb_link_node(&rmap_item->node, parent, new); rb_insert_color(&rmap_item->node, &root_unstable_tree); + ksm_pages_unshared++; return NULL; } @@ -1091,6 +1105,8 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) if (!err) { rb_erase(&tree_rmap_item->node, &root_unstable_tree); tree_rmap_item->address &= ~NODE_FLAG; + ksm_pages_unshared--; + /* * If we fail to insert the page into the stable tree, * we will have 2 virtual addresses that are pointing @@ -1474,6 +1490,37 @@ static ssize_t pages_sharing_show(struct kobject *kobj, } KSM_ATTR_RO(pages_sharing); +static ssize_t pages_unshared_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", ksm_pages_unshared); +} +KSM_ATTR_RO(pages_unshared); + +static ssize_t pages_volatile_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + long ksm_pages_volatile; + + ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared + - ksm_pages_sharing - ksm_pages_unshared; + /* + * It was not worth any locking to calculate that statistic, + * but it might therefore sometimes be negative: conceal that. + */ + if (ksm_pages_volatile < 0) + ksm_pages_volatile = 0; + return sprintf(buf, "%ld\n", ksm_pages_volatile); +} +KSM_ATTR_RO(pages_volatile); + +static ssize_t full_scans_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", ksm_scan.seqnr); +} +KSM_ATTR_RO(full_scans); + static struct attribute *ksm_attrs[] = { &sleep_millisecs_attr.attr, &pages_to_scan_attr.attr, @@ -1481,6 +1528,9 @@ static struct attribute *ksm_attrs[] = { &max_kernel_pages_attr.attr, &pages_shared_attr.attr, &pages_sharing_attr.attr, + &pages_unshared_attr.attr, + &pages_volatile_attr.attr, + &full_scans_attr.attr, NULL, }; -- 2.30.2