Hi guys,
This is rather a trivial change but is not for 2.6.0.
The patch is actually on top of some of my HT stuff so one part is
slightly different, but its purpose is to gather feedback.

It turns the cpu_sibling_map array from an array of cpus to an array
of cpumasks. This allows handling of more than 2 siblings, not that
I know of any immediate need.

I think it generalises cpu_sibling_map sufficiently that it can become
generic code. This would allow architecture specific code to build the
sibling map, and then Ingo's or my HT implementations to build their
scheduling descriptions in generic code.

I'm not aware of any reason why the kernel should not become generally
SMT aware. It is sufficiently different to SMP that it is worth
specialising it, although I am only aware of P4 and POWER5 implementations.

Best regards
Nick

P.S.
I have an alternative to Ingo's HT scheduler which basically does
the same thing. It is showing a 20% elapsed time improvement with a
make -j3 on a 2xP4 Xeon (4 logical CPUs).

Before Ingo's is merged, I would like to discuss the pros and cons of
both approaches with those interested. If Ingo's is accepted I should
still be able to port my other SMP/NUMA improvements on top of it.