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DateWed, 24 Jun 2009 17:13:37 -0700
From"H. Peter Anvin" <>
SubjectRe: [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support
Andi Kleen wrote:
>
> Haven't read the new patches, but per cpu data always was sized
> for all possible CPUs.
>
>> and N is large, what did it cost?
>
>> And what are reasonable values of N?
>
> N should normally not be large anymore, since num_possible_cpus()
> is sized based on firmware information now.
>

*Ahem* virtual machines *ahem*...

I have discussed this with Tejun, and the plan is to allocate the percpu
information when a processor is first brought online (but not removed
when it is offlined again.) It's a real problem for 32-bit VMs, so it's
more important than you'd think.

-hpa



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