Commit 03e404af authored by Christoph Lameter's avatar Christoph Lameter Committed by Pekka Enberg
Browse files

slub: fast release on full slab 



Make deactivation occur implicitly while checking out the current freelist.

This avoids one cmpxchg operation on a slab that is now fully in use.

Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
parent e36a2652

include/linux/slub_def.h

+1 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ enum stat_item { 
	DEACTIVATE_TO_HEAD,	/* Cpu slab was moved to the head of partials */

	DEACTIVATE_TO_TAIL,	/* Cpu slab was moved to the tail of partials */

	DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */

	DEACTIVATE_BYPASS,	/* Implicit deactivation */

	ORDER_FALLBACK,		/* Number of times fallback was necessary */

	CMPXCHG_DOUBLE_CPU_FAIL,/* Failure of this_cpu_cmpxchg_double */

	CMPXCHG_DOUBLE_FAIL,	/* Number of times that cmpxchg double did not match */

mm/slub.c

+19 −2
Original line number Diff line number Diff line
@@ -1977,9 +1977,21 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, 
		object = page->freelist;

		counters = page->counters;

		new.counters = counters;

		new.inuse = page->objects;

		VM_BUG_ON(!new.frozen);



		/*

		 * If there is no object left then we use this loop to

		 * deactivate the slab which is simple since no objects

		 * are left in the slab and therefore we do not need to

		 * put the page back onto the partial list.

		 *

		 * If there are objects left then we retrieve them

		 * and use them to refill the per cpu queue.

		*/



		new.inuse = page->objects;

		new.frozen = object != NULL;



	} while (!cmpxchg_double_slab(s, page,

			object, counters,

			NULL, new.counters,
@@ -1988,8 +2000,11 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, 
load_freelist:

	VM_BUG_ON(!page->frozen);



	if (unlikely(!object))

	if (unlikely(!object)) {

		c->page = NULL;

		stat(s, DEACTIVATE_BYPASS);

		goto new_slab;

	}



	stat(s, ALLOC_REFILL);
@@ -4680,6 +4695,7 @@ STAT_ATTR(DEACTIVATE_EMPTY, deactivate_empty); 
STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head);

STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail);

STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees);

STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);

STAT_ATTR(ORDER_FALLBACK, order_fallback);

STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);

STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
@@ -4740,6 +4756,7 @@ static struct attribute *slab_attrs[] = { 
	&deactivate_to_head_attr.attr,

	&deactivate_to_tail_attr.attr,

	&deactivate_remote_frees_attr.attr,

	&deactivate_bypass_attr.attr,

	&order_fallback_attr.attr,

	&cmpxchg_double_fail_attr.attr,

	&cmpxchg_double_cpu_fail_attr.attr,