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    SubjectRe: [RFC 0/2] ABI for clock_gettime_ns
    On Fri, Dec 23, 2011 at 10:50 PM, Richard Cochran
    <> wrote:
    > On Fri, Dec 23, 2011 at 09:59:04PM -0800, Andy Lutomirski wrote:
    >> I've written the patch and it's not as big an improvement as I hoped.
    >> I'll play with it a bit and send it out soon.
    > Andy, can you say what the motivation or use case is?

    Simplicity and performance. Many users (e.g. I) use clock_gettime to
    measure elapsed time. We just end up converting to flat nanoseconds
    over and over. This syscall avoids the conversion.

    The added padding bits will allow UTC/TAI offset and/or sub-nanosecond
    precision in the future if someone wants to add them.

    I seem to be saving just over one nanosecond per call on my laptop,
    which isn't that impressive. The real-world improvement may be better
    -- calling clock_gettime in a tight loop should give very good branch
    prediction success, which will make the cost of the loops that flat ns
    avoids seem a little lower than they are.

    I'll send patches in the morning.


    > Just curious,
    > Richard

    Andy Lutomirski
    AMA Capital Management, LLC
    Office: (310) 553-5322
    Mobile: (650) 906-0647

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