Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2009-09-21 at 17:10 +0100, Mel Gorman wrote:
> 
> It needs signed-off from the powerpc side because it's now allocating
> more
> memory potentially (Ben?). An alternative to this patch is in V1 that
> statically declares the per-node structures but this is potentially
> sub-optimal but from a performance and memory utilisation perspective.

So if I understand correctly, we have a problem with both cpu-less and
memory-less nodes. Interesting setups :-)

I have no strong objection on the allocating of the per-cpu data for
the cpu-less nodes. However, I wonder if we should do that a bit more
nicely, maybe with some kind of "adjusted" cpu_possible_mask() (could be
something like cpu_node_valid_mask or similar) to be used by percpu.

Mostly because it would be nice to have built-in debug features in
per-cpu and in that case, it would need some way to know a valid
number from an invalid one). Either that or just keep track of the
mask of cpus that had percpu data allocated to them

Cheers,
Ben.