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    SubjectRe: SMP syncronization on AMD processors (broken?)
    Andi Kleen a écrit :
    > Kirill Korotaev <> writes:
    >>Please help with a not simple question about spin_lock/spin_unlock on
    >>SMP archs. The question is whether concurrent spin_lock()'s should
    >>acquire it in more or less "fair" fashinon or one of CPUs can starve
    >>any arbitrary time while others do reacquire it in a loop.
    > They are not fully fair because of the NUMAness of the system.
    > Same on many other NUMA systems.
    > We considered long ago to use queued locks to avoid this, but
    > they are quite costly for the uncongested case and never seemed worth it.
    > So live with it.

    Unrelated, but that reminds me that current spinlock implementation on x86
    imply that NR_CPUS should be < 128.

    Maybe we should reflect this in Kconfig ?

    config NR_CPUS
    range 2 128

    Or use a plain int for spinlock, instead of a signed char.

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      Last update: 2005-10-06 15:53    [W:0.031 / U:1.292 seconds]
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