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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree [message #47921 is a reply to message #47902]

Tue, 18 September 2012 15:28

Christoph Lameter
Messages: 123
Registered: September 2006

Senior Member

On Tue, 18 Sep 2012, Glauber Costa wrote:

> index f2d760c..18de3f6 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3938,9 +3938,12 @@ EXPORT_SYMBOL(__kmalloc);
> * Free an object which was previously allocated from this
> * cache.
> */
> -void kmem_cache_free(struct kmem_cache *cachep, void *objp)
> +void kmem_cache_free(struct kmem_cache *s, void *objp)
> {
> unsigned long flags;
> + struct kmem_cache *cachep = virt_to_cache(objp);
> +
> + VM_BUG_ON(!slab_equal_or_parent(cachep, s));
>

This is an extremely hot path of the kernel and you are adding significant
processing. Check how the benchmarks are influenced by this change.
virt_to_cache can be a bit expensive.

> diff --git a/mm/slub.c b/mm/slub.c
> index 4778548..a045dfc 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2604,7 +2604,9 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
>
> page = virt_to_head_page(x);
>
> - slab_free(s, page, x, _RET_IP_);
> + VM_BUG_ON(!slab_equal_or_parent(page->slab, s));
> +
> + slab_free(page->slab, page, x, _RET_IP_);
>

Less of a problem here but you are eroding one advantage that slab has had
in the past over slub in terms of freeing objects.

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[Message index]

		[PATCH v3 00/16] slab accounting for memcg By: Glauber Costa on Tue, 18 September 2012 14:11
		[PATCH v3 02/16] slub: use free_page instead of put_page for freeing kmalloc allocation By: Glauber Costa on Tue, 18 September 2012 14:11
		[PATCH v3 01/16] slab/slub: struct memcg_params By: Glauber Costa on Tue, 18 September 2012 14:11
		[PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation By: Glauber Costa on Tue, 18 September 2012 14:11
		Re: [PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation By: Christoph Lameter on Tue, 18 September 2012 15:20
		Re: [PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation By: Tejun Heo on Fri, 21 September 2012 17:33
		[PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Christoph Lameter on Tue, 18 September 2012 15:28
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Glauber Costa on Wed, 19 September 2012 07:42
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Christoph Lameter on Wed, 19 September 2012 14:14
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Pekka Enberg on Fri, 21 September 2012 09:33
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Glauber Costa on Fri, 21 September 2012 09:30
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Pekka Enberg on Fri, 21 September 2012 09:41
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Tejun Heo on Fri, 21 September 2012 20:07
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Pekka Enberg on Fri, 21 September 2012 20:14
		Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree By: Tejun Heo on Fri, 21 September 2012 20:16
		[PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Tejun Heo on Fri, 21 September 2012 18:32
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Glauber Costa on Mon, 24 September 2012 08:46
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Tejun Heo on Mon, 24 September 2012 17:56
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Glauber Costa on Tue, 25 September 2012 13:57
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Christoph Lameter on Tue, 25 September 2012 16:28
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Tejun Heo on Fri, 21 September 2012 20:52
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Glauber Costa on Mon, 24 September 2012 08:17
		Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache By: Tejun Heo on Mon, 24 September 2012 17:58
		[PATCH v3 04/16] provide a common place for initcall processing in kmem_cache By: Glauber Costa on Tue, 18 September 2012 14:11
		Re: [PATCH v3 04/16] provide a common place for initcall processing in kmem_cache By: Christoph Lameter on Tue, 18 September 2012 15:22
		[PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions By: Tejun Heo on Fri, 21 September 2012 19:59
		Re: [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions By: Glauber Costa on Mon, 24 September 2012 09:09
		Re: [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions By: Tejun Heo on Mon, 24 September 2012 17:47
		[PATCH v3 12/16] memcg/sl[au]b Track all the memcg children of a kmem_cache. By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 12/16] memcg/sl[au]b Track all the memcg children of a kmem_cache. By: Tejun Heo on Fri, 21 September 2012 20:31
		[PATCH v3 14/16] slub: slub-specific propagation changes. By: Glauber Costa on Tue, 18 September 2012 14:12
		[PATCH v3 16/16] Add documentation about the kmem controller By: Glauber Costa on Tue, 18 September 2012 14:12
		[PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables By: Christoph Lameter on Tue, 18 September 2012 15:25
		Re: [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables By: Glauber Costa on Wed, 19 September 2012 07:44
		Re: [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables By: Pekka Enberg on Fri, 21 September 2012 09:29
		[PATCH v3 10/16] sl[au]b: Allocate objects from memcg cache By: Glauber Costa on Tue, 18 September 2012 14:12
		[PATCH v3 13/16] slab: slab-specific propagation changes. By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 13/16] slab: slab-specific propagation changes. By: Christoph Lameter on Tue, 18 September 2012 17:00
		Re: [PATCH v3 13/16] slab: slab-specific propagation changes. By: Glauber Costa on Wed, 19 September 2012 07:41
		[PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Glauber Costa on Tue, 18 September 2012 14:11
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Tejun Heo on Fri, 21 September 2012 18:14
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Glauber Costa on Mon, 24 September 2012 08:12
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: christoph on Mon, 24 September 2012 12:41
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Glauber Costa on Mon, 24 September 2012 12:41
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Christoph Lameter on Mon, 24 September 2012 13:42
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Glauber Costa on Mon, 24 September 2012 13:44
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Christoph Lameter on Mon, 24 September 2012 13:56
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Glauber Costa on Mon, 24 September 2012 13:57
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Pekka Enberg on Mon, 24 September 2012 15:38
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Glauber Costa on Mon, 24 September 2012 15:36
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Christoph Lameter on Mon, 24 September 2012 17:38
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Christoph Lameter on Mon, 24 September 2012 17:39
		Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache By: Michal Hocko on Tue, 02 October 2012 14:46
		[PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Christoph Lameter on Tue, 18 September 2012 17:02
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Glauber Costa on Wed, 19 September 2012 07:40
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Glauber Costa on Fri, 21 September 2012 08:40
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: JoonSoo Kim on Fri, 21 September 2012 09:28
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Glauber Costa on Fri, 21 September 2012 09:31
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Tejun Heo on Fri, 21 September 2012 20:40
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Glauber Costa on Mon, 24 September 2012 08:25
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: Tejun Heo on Mon, 24 September 2012 17:43
		Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches By: JoonSoo Kim on Fri, 21 September 2012 04:48
		[PATCH v3 11/16] memcg: destroy memcg caches By: Glauber Costa on Tue, 18 September 2012 14:12
		Re: [PATCH v3 11/16] memcg: destroy memcg caches By: Tejun Heo on Fri, 21 September 2012 20:22
		Re: [PATCH v3 00/16] slab accounting for memcg By: Pekka Enberg on Fri, 21 September 2012 09:40
		Re: [PATCH v3 00/16] slab accounting for memcg By: Glauber Costa on Fri, 21 September 2012 09:43
		Re: [PATCH v3 00/16] slab accounting for memcg By: Tejun Heo on Fri, 21 September 2012 20:46
		Re: [PATCH v3 00/16] slab accounting for memcg By: Tejun Heo on Fri, 21 September 2012 20:47
		Re: [PATCH v3 00/16] slab accounting for memcg By: Glauber Costa on Mon, 24 September 2012 08:15

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