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    Subject[my_cpu_ptr 0/5] Introduce my_cpu_ptr/__my_cpu_ptr
    The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
    an array lookup to find the offset for the cpu. Processors typically
    have the offset for the current cpu area already in some kind of
    (arch dependent) efficiently accessible register or memory location.

    We can use the per cpu offset instead of doing the array lookup to speed up the
    determination of the address of the percpu variable. This is particularly
    significant because these lookups occur in performance critical paths
    of the core kernel.

    This optimization is a prerequiste to the introduction of per processor
    atomic operations for the core code. Atomic per processor operations
    implicitly do the offset calculation to the current per cpu area in a
    single instruction. The locations touched by this patchset are potential
    candidates for atomic per cpu operations.

    The patchset does not cover arch code nor exotic cases where the current
    cpu is determined before the call into a function.

    --


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