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    SubjectRe: FOR REVIEW: New x86-64 vsyscall vgetcpu()
    Date
    On Monday 19 June 2006 02:15, Paul Jackson wrote:

    >
    > Roughly, he was looking to support something resembling the kernel's
    > per-cpu data in userland library code for high performance scientific
    > number crunching, for things like statistics gathering and perhaps (not
    > sure of this) reduce locking costs.

    While vgetcpu() can be used for this most likely glibc TLS is already
    good enough for this. So it will help, but I don't think it's the primary
    motivation.

    > I see "x86-64" in the Subject. I don't see why this facility is
    > arch-specific. Could it work on any arch, ia64 being the one of
    > interest to me?

    The implementation is x86-64 specific and optimized for x86-64. You could
    probably implement something with the same prototype for IA64 too,
    although the internal implementation will likely be very different
    (there is nothing x86-64 specific in the prototype)

    AFAIK ia64 supports fast system calls so it might be possible to
    do a simple implementation without vsyscalls.

    > I have some ignorance on your references to "CPUID(1)". I don't recall
    > what it is. The only command so named I find on my systems are a

    CPUID 1 is a x86 instruction that is one way to implement a user level
    vgetcpu on x86.

    -Andi
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