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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: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Lameter 2007-10-16 01:26:09 -07:00 committed by Linus Torvalds
parent 4c93c355d5
commit 42a9fdbb12
2 changed files with 13 additions and 2 deletions
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1
include/linux/slub_def.h
View File

@ -16,6 +16,7 @@ struct kmem_cache_cpu {
struct page *page;
int node;
unsigned int offset;
unsigned int objsize;
};
struct kmem_cache_node {

14
mm/slub.c
View File

@ -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))