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SubjectRe: [RFC] bitmap relative operator for mempolicy extensions
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On Thursday 14 February 2008 21:25:59 Mike Travis wrote:
> Christoph Lameter wrote:
> > On Thu, 14 Feb 2008, Andi Kleen wrote:
> >
> >> You're saying the kernel should use these relative masks internally?
> >
> > There is just some thoughts about this. Did not have time to look into the
> > details. Mike?
>
> There are a few places where the entire cpumask is not needed. For
> example, in the area of core siblings on a node. There's a limit
> to how many cores/threads can be on a node and the full 4k cpumask
> is not needed. How this pertains to this new functionality I'm
> not sure yet.

That would require that the BIOS enumerates the CPUs in a way that
the cores of a socket are continuous. While that's usually true
I don't think there's a guarantee. In theory they could be all scattered.

Ok I theory Linux could remap later but that seems hardly worth
the trouble.

I would rather just use arrays of integers in this case with a reasonable fixed
upper limit (e.g. 16 or 32 -- if there are ever >32 thread x86 CPUs presumably they will
require an updated cpufreq driver too...)


-Andi



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