Re: [PATCH 4/4] slub: deactivate freelist of kmem_cache_cpu all atonce in deactivate_slab()

[JoonSoo Kim]

2012/6/9 Christoph Lameter <cl@xxxxxxxxx>:
> 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.
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