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    SubjectRe: [PATCH 0/6] x86-64: Micro-optimize vclock_gettime

    * Andy Lutomirski <luto@mit.edu> wrote:

    > This series speeds up vclock_gettime(CLOCK_MONOTONIC) on by almost 30%
    > (tested on Sandy Bridge). They're ordered in roughly decreasing order
    > of improvement.
    >
    > These are meant for 2.6.40, but if anyone wants to take some of them
    > for 2.6.39 I won't object.
    >
    > The changes and timings (fastest of 20 trials of 100M iters on Sandy
    > Bridge) are:
    >
    > Unpatched:
    >
    > CLOCK_MONOTONIC: 22.09ns
    > CLOCK_REALTIME_COARSE: 4.23ns
    > CLOCK_MONOTONIC_COARSE: 5.65ns

    [ Patched: ]

    > CLOCK_MONOTONIC: 15.66ns
    > CLOCK_REALTIME_COARSE: 3.44ns
    > CLOCK_MONOTONIC_COARSE: 4.23ns

    That looks like a nice speedup, and speedups are definitely welcome. Many of
    your speedup patches were framed in an unclean or hard to maintain fashion
    though - so those have to be improved for this series to become palatable.

    Thanks,

    Ingo


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