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Commit 42a9fdbb authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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SLUB: Optimize cacheline use for zeroing 



We touch a cacheline in the kmem_cache structure for zeroing to get the
size. However, the hot paths in slab_alloc and slab_free do not reference
any other fields in kmem_cache, so we may have to just bring in the
cacheline for this one access.

Add a new field to kmem_cache_cpu that contains the object size. That
cacheline must already be used in the hotpaths. So we save one cacheline
on every slab_alloc if we zero.

We need to update the kmem_cache_cpu object size if an aliasing operation
changes the objsize of an non debug slab.

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 4c93c355

include/linux/slub_def.h

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ struct kmem_cache_cpu { 
	struct page *page;

	int node;

	unsigned int offset;

	unsigned int objsize;

};



struct kmem_cache_node {

mm/slub.c

+12 −2
Original line number Diff line number Diff line
@@ -1576,7 +1576,7 @@ static void __always_inline *slab_alloc(struct kmem_cache *s, 
	local_irq_restore(flags);



	if (unlikely((gfpflags & __GFP_ZERO) && object))

		memset(object, 0, s->objsize);

		memset(object, 0, c->objsize);



	return object;

}
@@ -1858,8 +1858,9 @@ static void init_kmem_cache_cpu(struct kmem_cache *s, 
{

	c->page = NULL;

	c->freelist = NULL;

	c->offset = s->offset / sizeof(void *);

	c->node = 0;

	c->offset = s->offset / sizeof(void *);

	c->objsize = s->objsize;

}



static void init_kmem_cache_node(struct kmem_cache_node *n)
@@ -2852,12 +2853,21 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size, 
	down_write(&slub_lock);

	s = find_mergeable(size, align, flags, name, ctor);

	if (s) {

		int cpu;



		s->refcount++;

		/*

		 * Adjust the object sizes so that we clear

		 * the complete object on kzalloc.

		 */

		s->objsize = max(s->objsize, (int)size);



		/*

		 * And then we need to update the object size in the

		 * per cpu structures

		 */

		for_each_online_cpu(cpu)

			get_cpu_slab(s, cpu)->objsize = s->objsize;

		s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));

		up_write(&slub_lock);

		if (sysfs_slab_alias(s, name))