Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK

[Christoph Lameter]

On Mon, 1 Oct 2007, Andrew Morton wrote:

> Do slab and slub use the same underlying page size for each slab?

SLAB cannot pack objects as dense as SLUB and they have different 
algorithm to make the choice of order. Thus the number of objects per slab 
may vary between SLAB and SLUB and therefore also the choice of order to 
store these objects.

> Single data point: the CONFIG_SLAB boxes which I have access to here are
> using order-0 for radix_tree_node, so they won't be failing in the way in
> which Peter's machine is.

Upstream SLUB uses order 0 allocations for the radix tree. MM varies 
because the use of higher order allocs is more loose if the mobility 
algorithms are found to be active:

2.6.23-rc8:

Name                   Objects Objsize    Space Slabs/Part/Cpu  O/S O %Fr %Ef Flg\
radix_tree_node          14281     552     9.9M     2432/948/1    7 0  38  79

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