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Commit 473b0ce4 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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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: default avatarHugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: default avatarIzik Eidus <ieidus@redhat.com>
Acked-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e178dfde

mm/ksm.c

+51 −1
Original line number Diff line number Diff line
@@ -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,

};