linux-kernel - Re: [PATCH 4/4] slub: deactivate freelist of kmem_cache_cpu all at once in deactivate

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Date:	Sat, 23 Jun 2012 03:34:27 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pekka Enberg <penberg@...nel.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 4/4] slub: deactivate freelist of kmem_cache_cpu all at
 once in deactivate_slab()

2012/6/10 JoonSoo Kim <js1304@...il.com>:
> 2012/6/9 Christoph Lameter <cl@...ux.com>:
>> On Sat, 9 Jun 2012, Joonsoo Kim wrote:
>>
>>> Current implementation of deactivate_slab() which deactivate
>>> freelist of kmem_cache_cpu one by one is inefficient.
>>> This patch changes it to deactivate freelist all at once.
>>> But, there is no overall performance benefit,
>>> because deactivate_slab() is invoked infrequently.
>>
>> Hmm, deactivate freelist can race with slab_free. Need to look at this in
>> detail.
>
> Implemented logic is nearly same as previous one.
> I just merge first step of previous deactivate_slab() with second one.
> In case of failure of cmpxchg_double_slab(), reloading page->freelist,
> page->counters and recomputing inuse
> ensure that race with slab_free() cannot be possible.
> In case that we need a lock, try to get a lock before invoking
> cmpxchg_double_slab(),
> so race with slab_free cannot be occured too.
>
> Above is my humble opinion, please give me some comments.

Hi Pekka and Christoph.
Could you give me some comments about this, please?
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