Re: [RFC] slub: Simplify boot kmem_cache_cpu allocations

[Christoph Lameter <cl@linux-foundation.org>]

On Thu, 17 Jun 2010, Tejun Heo wrote:

> 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?

Behavior is undefined. slab_is_available() determines if slab is up yet.

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