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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches [message #48002 is a reply to message #47989]

Mon, 24 September 2012 08:25

Glauber Costa
Messages: 916
Registered: October 2011

Senior Member

On 09/22/2012 12:40 AM, Tejun Heo wrote:
> Hello, Glauber.
>
> On Tue, Sep 18, 2012 at 06:12:09PM +0400, Glauber Costa wrote:
>> @@ -764,10 +777,21 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>> goto out;
>> }
>>
>> + /*
>> + * Because the cache is expected to duplicate the string,
>> + * we must make sure it has opportunity to copy its full
>> + * name. Only now we can remove the dead part from it
>> + */
>> + name = (char *)new_cachep->name;
>> + if (name)
>> + name[strlen(name) - 4] = '\0';
>
> This is kinda nasty. Do we really need to do this? How long would a
> dead cache stick around?

Without targeted shrinking, until all objects are manually freed, which
may need to wait global reclaim to kick in.

In general, if we agree with duplicating the caches, the problem that
they may stick around for some time will not be avoidable. If you have
any suggestions about alternative ways for it, I'm all ears.

>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index bd9928f..6cb4abf 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -3785,6 +3785,8 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp,
>> }
>>
>> ac_put_obj(cachep, ac, objp);
>> +
>> + kmem_cache_verify_dead(cachep);
>
> Reaping dead caches doesn't exactly sound like a high priority thing
> and adding a branch to hot path for that might not be the best way to
> do it. Why not schedule an extremely lazy deferrable delayed_work
> which polls for emptiness, say, every miniute or whatever?
>

Because this branch is marked as unlikely, I would expect it not to be a
big problem. It will be not taken most of the time, and becomes a very
cheap branch. I considered this to be simpler than a deferred work
mechanism.

If even then, you guys believe this is still too high, I can resort to that.

> Thanks.
>

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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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