Commit e95eed57 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

SLUB: Add MIN_PARTIAL 



We leave a mininum of partial slabs on nodes when we search for
partial slabs on other node. Define a constant for that value.

Then modify slub to keep MIN_PARTIAL slabs around.

This avoids bad situations where a function frees the last object
in a slab (which results in the page being returned to the page
allocator) only to then allocate one again (which requires getting
a page back from the page allocator if the partial list was empty).
Keeping a couple of slabs on the partial list reduces overhead.

Empty slabs are added to the end of the partial list to insure that
partially allocated slabs are consumed first (defragmentation).

Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 53e15af0

mm/slub.c

+36 −19
Original line number Diff line number Diff line
@@ -133,6 +133,9 @@ 
 */

#define SLUB_UNIMPLEMENTED (SLAB_DEBUG_INITIAL)



/* Mininum number of partial slabs */

#define MIN_PARTIAL 2



#define DEBUG_DEFAULT_FLAGS (SLAB_DEBUG_FREE | SLAB_RED_ZONE | \

				SLAB_POISON | SLAB_STORE_USER)

/*
@@ -664,16 +667,8 @@ static int on_freelist(struct kmem_cache *s, struct page *page, void *search) 
/*

 * Tracking of fully allocated slabs for debugging

 */

static void add_full(struct kmem_cache *s, struct page *page)

static void add_full(struct kmem_cache_node *n, struct page *page)

{

	struct kmem_cache_node *n;



	VM_BUG_ON(!irqs_disabled());



	if (!(s->flags & SLAB_STORE_USER))

		return;



	n = get_node(s, page_to_nid(page));

	spin_lock(&n->list_lock);

	list_add(&page->lru, &n->full);

	spin_unlock(&n->list_lock);
@@ -982,10 +977,16 @@ static __always_inline int slab_trylock(struct page *page) 
/*

 * Management of partially allocated slabs

 */

static void add_partial(struct kmem_cache *s, struct page *page)

static void add_partial_tail(struct kmem_cache_node *n, struct page *page)

{

	struct kmem_cache_node *n = get_node(s, page_to_nid(page));

	spin_lock(&n->list_lock);

	n->nr_partial++;

	list_add_tail(&page->lru, &n->partial);

	spin_unlock(&n->list_lock);

}



static void add_partial(struct kmem_cache_node *n, struct page *page)

{

	spin_lock(&n->list_lock);

	n->nr_partial++;

	list_add(&page->lru, &n->partial);
@@ -1085,7 +1086,7 @@ static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags) 
		n = get_node(s, zone_to_nid(*z));



		if (n && cpuset_zone_allowed_hardwall(*z, flags) &&

				n->nr_partial > 2) {

				n->nr_partial > MIN_PARTIAL) {

			page = get_partial_node(n);

			if (page)

				return page;
@@ -1119,17 +1120,33 @@ static struct page *get_partial(struct kmem_cache *s, gfp_t flags, int node) 
 */

static void putback_slab(struct kmem_cache *s, struct page *page)

{

	struct kmem_cache_node *n = get_node(s, page_to_nid(page));



	if (page->inuse) {



		if (page->freelist)

			add_partial(s, page);

		else if (PageError(page))

			add_full(s, page);

			add_partial(n, page);

		else if (PageError(page) && (s->flags & SLAB_STORE_USER))

			add_full(n, page);

		slab_unlock(page);



	} else {

		if (n->nr_partial < MIN_PARTIAL) {

			/*

			 * Adding an empty page to the partial slabs in order

			 * to avoid page allocator overhead. This page needs to

			 * come after all the others that are not fully empty

			 * in order to make sure that we do maximum

			 * defragmentation.

			 */

			add_partial_tail(n, page);

			slab_unlock(page);

		} else {

			slab_unlock(page);

			discard_slab(s, page);

		}

	}

}



/*

 * Remove the cpu slab
@@ -1326,7 +1343,7 @@ checks_ok: 
	 * then add it.

	 */

	if (unlikely(!prior))

		add_partial(s, page);

		add_partial(get_node(s, page_to_nid(page)), page);



out_unlock:

	slab_unlock(page);
@@ -1535,7 +1552,7 @@ static struct kmem_cache_node * __init early_kmem_cache_node_alloc(gfp_t gfpflag 
	init_object(kmalloc_caches, n, 1);

	init_kmem_cache_node(n);

	atomic_long_inc(&n->nr_slabs);

	add_partial(kmalloc_caches, page);

	add_partial(n, page);

	return n;

}

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