Commit 97654dfa authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds
Browse files

slab: defer slab_destroy in free_block() 



In free_block(), if freeing object makes new free slab and number of
free_objects exceeds free_limit, we start to destroy this new free slab
with holding the kmem_cache node lock.  Holding the lock is useless and,
generally, holding a lock as least as possible is good thing.  I never
measure performance effect of this, but we'd be better not to hold the
lock as much as possible.

Commented by Christoph:
  This is also good because kmem_cache_free is no longer called while
  holding the node lock. So we avoid one case of recursion.

Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: default avatarChristoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 25c063fb

mm/slab.c

+41 −19
Original line number Diff line number Diff line
@@ -242,7 +242,8 @@ static struct kmem_cache_node __initdata init_kmem_cache_node[NUM_INIT_LISTS]; 
static int drain_freelist(struct kmem_cache *cache,

			struct kmem_cache_node *n, int tofree);

static void free_block(struct kmem_cache *cachep, void **objpp, int len,

			int node);

			int node, struct list_head *list);

static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list);

static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp);

static void cache_reap(struct work_struct *unused);
@@ -1030,6 +1031,7 @@ static void __drain_alien_cache(struct kmem_cache *cachep, 
				struct array_cache *ac, int node)

{

	struct kmem_cache_node *n = get_node(cachep, node);

	LIST_HEAD(list);



	if (ac->avail) {

		spin_lock(&n->list_lock);
@@ -1041,9 +1043,10 @@ static void __drain_alien_cache(struct kmem_cache *cachep, 
		if (n->shared)

			transfer_objects(n->shared, ac, ac->limit);



		free_block(cachep, ac->entry, ac->avail, node);

		free_block(cachep, ac->entry, ac->avail, node, &list);

		ac->avail = 0;

		spin_unlock(&n->list_lock);

		slabs_destroy(cachep, &list);

	}

}
@@ -1087,6 +1090,7 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp) 
	struct kmem_cache_node *n;

	struct array_cache *alien = NULL;

	int node;

	LIST_HEAD(list);



	node = numa_mem_id();
@@ -1111,8 +1115,9 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp) 
	} else {

		n = get_node(cachep, nodeid);

		spin_lock(&n->list_lock);

		free_block(cachep, &objp, 1, nodeid);

		free_block(cachep, &objp, 1, nodeid, &list);

		spin_unlock(&n->list_lock);

		slabs_destroy(cachep, &list);

	}

	return 1;

}
@@ -1182,6 +1187,7 @@ static void cpuup_canceled(long cpu) 
		struct array_cache *nc;

		struct array_cache *shared;

		struct array_cache **alien;

		LIST_HEAD(list);



		/* cpu is dead; no one can alloc from it. */

		nc = cachep->array[cpu];
@@ -1196,7 +1202,7 @@ static void cpuup_canceled(long cpu) 
		/* Free limit for this kmem_cache_node */

		n->free_limit -= cachep->batchcount;

		if (nc)

			free_block(cachep, nc->entry, nc->avail, node);

			free_block(cachep, nc->entry, nc->avail, node, &list);



		if (!cpumask_empty(mask)) {

			spin_unlock_irq(&n->list_lock);
@@ -1206,7 +1212,7 @@ static void cpuup_canceled(long cpu) 
		shared = n->shared;

		if (shared) {

			free_block(cachep, shared->entry,

				   shared->avail, node);

				   shared->avail, node, &list);

			n->shared = NULL;

		}
@@ -1221,6 +1227,7 @@ static void cpuup_canceled(long cpu) 
			free_alien_cache(alien);

		}

free_array_cache:

		slabs_destroy(cachep, &list);

		kfree(nc);

	}

	/*
@@ -2056,6 +2063,16 @@ static void slab_destroy(struct kmem_cache *cachep, struct page *page) 
		kmem_cache_free(cachep->freelist_cache, freelist);

}



static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list)

{

	struct page *page, *n;



	list_for_each_entry_safe(page, n, list, lru) {

		list_del(&page->lru);

		slab_destroy(cachep, page);

	}

}



/**

 * calculate_slab_order - calculate size (page order) of slabs

 * @cachep: pointer to the cache that is being created
@@ -2459,13 +2476,15 @@ static void do_drain(void *arg) 
	struct array_cache *ac;

	int node = numa_mem_id();

	struct kmem_cache_node *n;

	LIST_HEAD(list);



	check_irq_off();

	ac = cpu_cache_get(cachep);

	n = get_node(cachep, node);

	spin_lock(&n->list_lock);

	free_block(cachep, ac->entry, ac->avail, node);

	free_block(cachep, ac->entry, ac->avail, node, &list);

	spin_unlock(&n->list_lock);

	slabs_destroy(cachep, &list);

	ac->avail = 0;

}
@@ -3393,9 +3412,10 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller) 


/*

 * Caller needs to acquire correct kmem_cache_node's list_lock

 * @list: List of detached free slabs should be freed by caller

 */

static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects,

		       int node)

static void free_block(struct kmem_cache *cachep, void **objpp,

			int nr_objects, int node, struct list_head *list)

{

	int i;

	struct kmem_cache_node *n = get_node(cachep, node);
@@ -3418,13 +3438,7 @@ static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects, 
		if (page->active == 0) {

			if (n->free_objects > n->free_limit) {

				n->free_objects -= cachep->num;

				/* No need to drop any previously held

				 * lock here, even if we have a off-slab slab

				 * descriptor it is guaranteed to come from

				 * a different cache, refer to comments before

				 * alloc_slabmgmt.

				 */

				slab_destroy(cachep, page);

				list_add_tail(&page->lru, list);

			} else {

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

			}
@@ -3443,6 +3457,7 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac) 
	int batchcount;

	struct kmem_cache_node *n;

	int node = numa_mem_id();

	LIST_HEAD(list);



	batchcount = ac->batchcount;

#if DEBUG
@@ -3464,7 +3479,7 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac) 
		}

	}



	free_block(cachep, ac->entry, batchcount, node);

	free_block(cachep, ac->entry, batchcount, node, &list);

free_done:

#if STATS

	{
@@ -3485,6 +3500,7 @@ free_done: 
	}

#endif

	spin_unlock(&n->list_lock);

	slabs_destroy(cachep, &list);

	ac->avail -= batchcount;

	memmove(ac->entry, &(ac->entry[batchcount]), sizeof(void *)*ac->avail);

}
@@ -3765,12 +3781,13 @@ static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp) 
		n = get_node(cachep, node);

		if (n) {

			struct array_cache *shared = n->shared;

			LIST_HEAD(list);



			spin_lock_irq(&n->list_lock);



			if (shared)

				free_block(cachep, shared->entry,

						shared->avail, node);

						shared->avail, node, &list);



			n->shared = new_shared;

			if (!n->alien) {
@@ -3780,6 +3797,7 @@ static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp) 
			n->free_limit = (1 + nr_cpus_node(node)) *

					cachep->batchcount + cachep->num;

			spin_unlock_irq(&n->list_lock);

			slabs_destroy(cachep, &list);

			kfree(shared);

			free_alien_cache(new_alien);

			continue;
@@ -3869,6 +3887,7 @@ static int __do_tune_cpucache(struct kmem_cache *cachep, int limit, 
	cachep->shared = shared;



	for_each_online_cpu(i) {

		LIST_HEAD(list);

		struct array_cache *ccold = new->new[i];

		int node;

		struct kmem_cache_node *n;
@@ -3879,8 +3898,9 @@ static int __do_tune_cpucache(struct kmem_cache *cachep, int limit, 
		node = cpu_to_mem(i);

		n = get_node(cachep, node);

		spin_lock_irq(&n->list_lock);

		free_block(cachep, ccold->entry, ccold->avail, node);

		free_block(cachep, ccold->entry, ccold->avail, node, &list);

		spin_unlock_irq(&n->list_lock);

		slabs_destroy(cachep, &list);

		kfree(ccold);

	}

	kfree(new);
@@ -3988,6 +4008,7 @@ skip_setup: 
static void drain_array(struct kmem_cache *cachep, struct kmem_cache_node *n,

			 struct array_cache *ac, int force, int node)

{

	LIST_HEAD(list);

	int tofree;



	if (!ac || !ac->avail)
@@ -4000,12 +4021,13 @@ static void drain_array(struct kmem_cache *cachep, struct kmem_cache_node *n, 
			tofree = force ? ac->avail : (ac->limit + 4) / 5;

			if (tofree > ac->avail)

				tofree = (ac->avail + 1) / 2;

			free_block(cachep, ac->entry, tofree, node);

			free_block(cachep, ac->entry, tofree, node, &list);

			ac->avail -= tofree;

			memmove(ac->entry, &(ac->entry[tofree]),

				sizeof(void *) * ac->avail);

		}

		spin_unlock_irq(&n->list_lock);

		slabs_destroy(cachep, &list);

	}

}

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