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| Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches [message #47966 is a reply to message #47913] |
Fri, 21 September 2012 08:40   |
Glauber Costa
Messages: 916
Registered: October 2011
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Senior Member |
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On 09/21/2012 08:48 AM, JoonSoo Kim wrote:
> Hi Glauber.
>
Hi
> 2012/9/18 Glauber Costa <glommer@parallels.com>:
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 0b68d15..9d79216 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -2602,6 +2602,7 @@ redo:
>> } else
>> __slab_free(s, page, x, addr);
>>
>> + kmem_cache_verify_dead(s);
>> }
>
> As far as u know, I am not a expert and don't know anything about memcg.
> IMHO, this implementation may hurt system performance in some case.
>
> In case of memcg is destoried, remained kmem_cache is marked "dead".
> After it is marked,
> every free operation to this "dead" kmem_cache call
> kmem_cache_verify_dead() and finally call kmem_cache_shrink().
As long as it is restricted to that cache, this is a non issue.
dead caches are exactly what they name imply: dead.
Means that we actively want them to go away, and just don't kill them
right away because they have some inflight objects - which we expect not
to be too much.
> kmem_cache_shrink() do invoking kmalloc and flush_all() and taking a
> lock for online node and invoking kfree.
> Especially, flush_all() may hurt performance largely, because it call
> has_cpu_slab() against all the cpus.
Again, this is all right, but being a dead cache, it shouldn't be on any
hot path.
>
> And, I found one case that destroying memcg's kmem_cache don't works properly.
> If we destroy memcg after all object is freed, current implementation
> doesn't destroy kmem_cache.
> kmem_cache_destroy_work_func() check "cachep->memcg_params.nr_pages == 0",
> but in this case, it return false, because kmem_cache may have
> cpu_slab, and cpu_partials_slabs.
> As we already free all objects, kmem_cache_verify_dead() is not invoked forever.
> I think that we need another kmem_cache_shrink() in
> kmem_cache_destroy_work_func().
I'll take a look here. What you describe makes sense, and can
potentially happen. I tried to handle this case with care in
destroy_all_caches, but I may have always made a mistake...
Did you see this actively happening, or are you just assuming this can
happen from your read of the code?
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[PATCH v3 00/16] slab accounting for memcg
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[PATCH v3 02/16] slub: use free_page instead of put_page for freeing kmalloc allocation
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[PATCH v3 01/16] slab/slub: struct memcg_params
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[PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation
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Re: [PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation
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Re: [PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation
By: Tejun Heo on Fri, 21 September 2012 17:33 |
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[PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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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 |
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Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
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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 |
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[PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache
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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 |
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Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache
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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 |
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Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache
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Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache
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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 |
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Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache
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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 |
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[PATCH v3 04/16] provide a common place for initcall processing in kmem_cache
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Re: [PATCH v3 04/16] provide a common place for initcall processing in kmem_cache
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[PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions
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Re: [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions
By: Tejun Heo on Fri, 21 September 2012 19:59 |
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Re: [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions
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Re: [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions
By: Tejun Heo on Mon, 24 September 2012 17:47 |
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[PATCH v3 12/16] memcg/sl[au]b Track all the memcg children of a kmem_cache.
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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 |
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[PATCH v3 14/16] slub: slub-specific propagation changes.
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[PATCH v3 16/16] Add documentation about the kmem controller
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[PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables
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Re: [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables
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Re: [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables
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Re: [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables
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[PATCH v3 10/16] sl[au]b: Allocate objects from memcg cache
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[PATCH v3 13/16] slab: slab-specific propagation changes.
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Re: [PATCH v3 13/16] slab: slab-specific propagation changes.
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Re: [PATCH v3 13/16] slab: slab-specific propagation changes.
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[PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
By: Tejun Heo on Fri, 21 September 2012 18:14 |
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
By: christoph on Mon, 24 September 2012 12:41 |
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache
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[PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
By: Tejun Heo on Fri, 21 September 2012 20:40 |
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
By: Tejun Heo on Mon, 24 September 2012 17:43 |
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Re: [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches
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[PATCH v3 11/16] memcg: destroy memcg caches
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Re: [PATCH v3 11/16] memcg: destroy memcg caches
By: Tejun Heo on Fri, 21 September 2012 20:22 |
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Re: [PATCH v3 00/16] slab accounting for memcg
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Re: [PATCH v3 00/16] slab accounting for memcg
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Re: [PATCH v3 00/16] slab accounting for memcg
By: Tejun Heo on Fri, 21 September 2012 20:46 |
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Re: [PATCH v3 00/16] slab accounting for memcg
By: Tejun Heo on Fri, 21 September 2012 20:47 |
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Re: [PATCH v3 00/16] slab accounting for memcg
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