Re: NUMA aware slab allocator V3

["Martin J. Bligh" <mbligh@mbligh.org>]

> Right, the SGI boxes have discontiguous memory within a node, but it's 
> not represented by pgdats (like you said, one 'virtual memmap' spans 
> the whole address space of a node).  Sparse can help simplify this 
> across platforms, but has the potential to be more expensive for 
> systems with dynamically sized holes, due to the additional calculation 
> and potential cache miss associated with indexing into the correct 
> memmap (Dave can probably correct me here, it's been awhile).  With a 
> virtual memmap, you only occasionally take a TLB miss on the struct 
> page access after indexing into the array.

That's exactly what was brilliant about Andy's code ... it fixed that,
there shouldn't be extra references ...
 
>> transition config options are a bit of a mess ... Andy, I presume
>> CONFIG_NEED_MULTIPLE_NODES is really CONFIG_NEED_MULTIPLE_PGDATS ?
> 
> Yeah, makes sense for the NUMA aware slab allocator to depend on 
> CONFIG_NUMA.

Andy confirmed offline that this is really CONFIG_NEED_MULTIPLE_PGDATS,
and is just named wrong.

M.