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    SubjectRe: gettimeofday resolution seriously degraded in test9
    >>>>> "Richard" == Richard B Johnson <root@chaos.analogic.com> writes:

    Richard> There isn't any magic that can solve this problem. It turns
    Richard> out that with later Intel CPUs, one can get CPU-clock
    Richard> resolution from rdtsc. However, this is hardware-specific. If
    Richard> somebody modifies the gettimeofday() and the POSIX clock
    Richard> routines to use rdtsc when available, a lot of problems will
    Richard> go away.

    gettimofday() and the posix clock routines (which use gettimeofday())
    *do* use rdtsc if the processor has a reliable one --- do_gettimeofday() calls
    cur_timer->get_offset(), which is essentially a scaled rdtsc if you're
    using timers_tsc.c.

    But when you have power management turned on, TSC doesn't run at a
    constant rate. If it gets *too* slow, the timer switches to use the
    PIT instead, and one loses the cycle-resolution one would otherwise have.

    --
    Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au
    You are lost in a maze of BitKeeper repositories, all slightly different.

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