From: Glauber Costa <glommer@parallels.com>
To: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux.com>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
kamezawa.hiroyu@jp.fujitsu.com, devel@openvz.org,
Tejun Heo <tj@kernel.org>,
linux-mm@kvack.org, Suleiman Souhlal <suleiman@google.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mel Gorman <mgorman@suse.de>,
David Rientjes <rientjes@google.com>, Ingo Molnar <mingo@elte.hu>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree
Date: Fri, 21 Sep 2012 13:30:59 +0400 [thread overview]
Message-ID: <505C33D3.5000202@parallels.com> (raw)
In-Reply-To: <CAOJsxLFgwOqUcLHEwYNERwn1Uvp4-8CmvRKTfBFAHD6p_-6c7g@mail.gmail.com>
On 09/21/2012 01:33 PM, Pekka Enberg wrote:
> On Wed, Sep 19, 2012 at 10:42 AM, Glauber Costa <glommer@parallels.com> 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.
>>
>> Would it be enough for you to have a separate code path for
>> !CONFIG_MEMCG_KMEM?
>>
>> I don't really see another way to do it, aside from deriving the cache
>> from the object in our case. I am open to suggestions if you do.
>
> We should assume that most distributions enable CONFIG_MEMCG_KMEM,
> right? Therfore, any performance impact should be dependent on whether
> or not kmem memcg is *enabled* at runtime or not.
>
> Can we use the "static key" thingy introduced by tracing folks for this?
>
Yes.
I am already using static keys extensively in this patchset, and that is
how I intend to handle this particular case.
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next prev parent reply other threads:[~2012-09-21 9:34 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-18 14:11 [PATCH v3 00/16] slab accounting for memcg Glauber Costa
2012-09-18 14:11 ` [PATCH v3 01/16] slab/slub: struct memcg_params Glauber Costa
2012-09-18 14:11 ` [PATCH v3 02/16] slub: use free_page instead of put_page for freeing kmalloc allocation Glauber Costa
2012-09-18 14:11 ` [PATCH v3 03/16] slab: Ignore the cflgs bit in cache creation Glauber Costa
2012-09-18 15:20 ` Christoph Lameter
2012-09-21 17:33 ` Tejun Heo
2012-09-18 14:11 ` [PATCH v3 04/16] provide a common place for initcall processing in kmem_cache Glauber Costa
2012-09-18 15:22 ` Christoph Lameter
2012-09-18 14:11 ` [PATCH v3 05/16] consider a memcg parameter in kmem_create_cache Glauber Costa
2012-09-21 18:14 ` Tejun Heo
2012-09-24 8:12 ` Glauber Costa
2012-09-24 12:41 ` Christoph
2012-09-24 12:41 ` Glauber Costa
2012-09-24 13:42 ` Christoph Lameter
2012-09-24 13:44 ` Glauber Costa
2012-09-24 13:56 ` Christoph Lameter
2012-09-24 13:57 ` Glauber Costa
2012-09-24 15:38 ` Pekka Enberg
2012-09-24 15:36 ` Glauber Costa
2012-09-24 17:38 ` Christoph Lameter
2012-09-24 17:39 ` Christoph Lameter
2012-10-02 14:46 ` Michal Hocko
2012-09-18 14:12 ` [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache Glauber Costa
2012-09-21 18:32 ` Tejun Heo
2012-09-24 8:46 ` Glauber Costa
2012-09-24 17:56 ` Tejun Heo
2012-09-25 13:57 ` Glauber Costa
2012-09-25 16:28 ` Christoph Lameter
2012-09-21 20:52 ` Tejun Heo
2012-09-24 8:17 ` Glauber Costa
2012-09-24 17:58 ` Tejun Heo
2012-09-18 14:12 ` [PATCH v3 07/16] memcg: skip memcg kmem allocations in specified code regions Glauber Costa
2012-09-21 19:59 ` Tejun Heo
2012-09-24 9:09 ` Glauber Costa
2012-09-24 17:47 ` Tejun Heo
2012-09-18 14:12 ` [PATCH v3 08/16] slab: allow enable_cpu_cache to use preset values for its tunables Glauber Costa
2012-09-18 15:25 ` Christoph Lameter
2012-09-19 7:44 ` Glauber Costa
2012-09-21 9:29 ` Pekka Enberg
2012-09-18 14:12 ` [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree Glauber Costa
2012-09-18 15:28 ` Christoph Lameter
2012-09-19 7:42 ` Glauber Costa
2012-09-19 14:14 ` Christoph Lameter
2012-09-21 9:33 ` Pekka Enberg
2012-09-21 9:30 ` Glauber Costa [this message]
2012-09-21 9:41 ` Pekka Enberg
2012-09-21 20:07 ` Tejun Heo
2012-09-21 20:14 ` Pekka Enberg
2012-09-21 20:16 ` Tejun Heo
2012-09-18 14:12 ` [PATCH v3 10/16] sl[au]b: Allocate objects from memcg cache Glauber Costa
2012-09-18 14:12 ` [PATCH v3 11/16] memcg: destroy memcg caches Glauber Costa
2012-09-21 20:22 ` Tejun Heo
2012-09-18 14:12 ` [PATCH v3 12/16] memcg/sl[au]b Track all the memcg children of a kmem_cache Glauber Costa
2012-09-21 20:31 ` Tejun Heo
2012-09-18 14:12 ` [PATCH v3 13/16] slab: slab-specific propagation changes Glauber Costa
2012-09-18 17:00 ` Christoph Lameter
2012-09-19 7:41 ` Glauber Costa
2012-09-18 14:12 ` [PATCH v3 14/16] slub: slub-specific " Glauber Costa
2012-09-18 14:12 ` [PATCH v3 15/16] memcg/sl[au]b: shrink dead caches Glauber Costa
2012-09-18 17:02 ` Christoph Lameter
2012-09-19 7:40 ` Glauber Costa
2012-09-21 4:48 ` JoonSoo Kim
2012-09-21 8:40 ` Glauber Costa
2012-09-21 9:28 ` JoonSoo Kim
2012-09-21 9:31 ` Glauber Costa
2012-09-21 20:40 ` Tejun Heo
2012-09-24 8:25 ` Glauber Costa
2012-09-24 17:43 ` Tejun Heo
2012-09-18 14:12 ` [PATCH v3 16/16] Add documentation about the kmem controller Glauber Costa
2012-09-21 9:40 ` [PATCH v3 00/16] slab accounting for memcg Pekka Enberg
2012-09-21 9:43 ` Glauber Costa
2012-09-21 20:46 ` Tejun Heo
2012-09-21 20:47 ` Tejun Heo
2012-09-24 8:15 ` Glauber Costa
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