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authorHugh Dickins <hugh.dickins@tiscali.co.uk>2009-09-21 17:02:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:32 -0700
commit473b0ce4d13ee77925a7062e25dea0d16a91f654 (patch)
tree965433f77af7ddce5d9911e353e13af6db9ea311 /mm/ksm.c
parentksm: move pages_sharing updates (diff)
downloadlinux-dev-473b0ce4d13ee77925a7062e25dea0d16a91f654.tar.xz
linux-dev-473b0ce4d13ee77925a7062e25dea0d16a91f654.zip
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 <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>
Diffstat (limited to '')
-rw-r--r--mm/ksm.c52
1 files changed, 51 insertions, 1 deletions
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,
};