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    On Fri, Jul 17, 2009 at 7:39 PM, john stultz<> wrote:
    > -       if (likely(gtod->sysctl_enabled && gtod->clock.vread))
    > +       if (likely(gtod->sysctl_enabled))

    This irks me. If the sysctl is enabled and the codepath is getting
    used often enough that we care about performance, branch prediction
    should do the right thing without compiler hints. On the other hand,
    if the sysctl is disabled, and the compiler is telling the cpu to
    ignore its branch predictor, it'll hurt. I don't think we should be
    wrapping (un)likely annotations around configuration options, unless
    we're biasing against debug conditions where we definitely don't care
    about performance. The patch is certainly no worse than the existing
    code, but while we have the hood up, it might be nice to remove the
    annotation, unless we're sure that it does no harm, and does some

    -- Chris
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