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    SubjectRe: [RFC] bitmap relative operator for mempolicy extensions
    Date
    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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