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    SubjectRe: [RFC] CPUMASK: proposal for replacing cpumask_t
    Mike Travis wrote:
    >
    > Here's the thread:
    >
    > http://marc.info/?l=linux-kernel&m=121976977901223&w=4
    >
    > It doesn't seem worthwhile to force all systems to deal with large cpumask's
    > if they don't need to. Passing the value on the stack (actually usually in a
    > reg) if it fits into a long makes a lot of sense.
    >
    > And I don't think it's that abstract, but I'm willing to hear other opinions.
    >
    > Btw, most likely only distros that distribute an "Enterprise" edition of
    > Linux will ever set NR_CPUS so high, so the actual number of systems making
    > use of this will be a very small percentage (big $$-wise though... ;-)
    >
    > I even think that perhaps BITS_PER_LONG might be too low a threshold to kick
    > in this extra code. A Larabee chip will have 128 cpus so maybe 128 or 256 is
    > a better metric...?
    >
    > As soon as I get a working kernel with the proposed changes, I will definitely
    > be doing perf testing.
    >

    If the performance difference isn't significant, then there is a major
    advantage to getting rid of a configuration option. At that point we
    can basically scale to an arbitrary number of processors in a stock
    configuration.

    -hpa



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