Re: [patch 2/5] slub: Fallback to kmalloc_large for failing higher order allocs

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

Christoph Lameter wrote:
> That would mean reducing the number of objects that can be allocated from 
> the fastpath before we have to go to the page allocator again. Increasing 
> the number of fastpath uses vs slowpath increases the overall performance 
> of a slab.
> 
> If we would use order 0 slab allocs for 4k slabs then every call to 
> slab_alloc would lead to a corresponding call to the page allocator. The 
> regression would not be fixed. We just add slab_alloc overhead to an 
> already bad page allocator call.

Aah, I see. I wonder if we can fix up allocate_slab() to try with a 
smaller order as long as the size allows that? The only problem I can 
see is s->objects but I think we can just move that to be a per-slab 
variable. So sort of variable-order slabs kind of a thing.

What do you think?

			Pekka

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