Re: [RFC] slub: Simplify boot kmem_cache_cpu allocations

[Pekka Enberg <penberg@cs.helsinki.fi>]

On 6/17/10 11:49 AM, Tejun Heo wrote:
> Hello,
>
> On 06/16/2010 07:35 PM, Christoph Lameter wrote:
>>> It's primarily controlled by PERCPU_DYNAMIC_RESERVE.  I don't think
>>> there will be any systematic way to do it other than sizing it
>>> sufficiently.  Can you calculate the upper bound?  The constant has
>>> been used primarily for optimization so how it's used needs to be
>>> audited if we wanna guarantee free space in the first chunk but I
>>> don't think it would be too difficult.
>>
>> The upper bound is SLUB_PAGE_SHIFT * sizeof(struct kmem_cache_cpu).
>>
>> Thats usually 14 * 104 bytes = 1456 bytes. This may increase to more
>> than 8k given the future plans to add queues into kmem_cache_cpu.
>
> Alright, will work on that.  Does slab allocator guarantee to return
> NULL if called before initialized or is it undefined?  If latter, is
> there a way to determine whether slab is initialized yet?

It's undefined and you can use slab_is_available() to check if it's 
available or not.

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