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SubjectRe: Optimisation for smp_num_cpus loop in hotplug
From said:
> This is neat, but I'd like to see it work with O(1) as well. Mingo's
> code uses some long bitmaps.

Well, it's strictly only for the cpu bitmap (and it's designed to be different
depending on the arch so you can use arch specific CPU enumeration knowlege).
The O(1) optimisation for this is easy:

#define for_each_cpu(cpu, mask) \
for(mask = cpu_online_map; \
cpu = __ffs(mask), mask != 0; \
mask &= ~(1<<cpu))
#define for_each_cpu(cpu, mask) cpu = 1;

because you don't really want to run an SMP kernel on a machine which has only
one cpu. Or did you mean you'd like to see it work with the O(1) scheduler,
some kind of generic for_each_set_bit?


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