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    SubjectRe: a faster way to gettimeofday?
    On Tue, 5 Mar 2002, Ben Greear wrote:

    >
    >
    > Davide Libenzi wrote:
    >
    > > On Tue, 5 Mar 2002, Ben Greear wrote:
    > >
    > >
    > >>I have a program that I very often need to calculate the current
    > >>time, with milisecond accuracy. I've been using gettimeofday(),
    > >>but gprof shows it's taking a significant (10% or so) amount of
    > >>time. Is there a faster (and perhaps less portable?) way to get
    > >>the time information on x86? My program runs as root, so should
    > >>have any permissions it needs to use some backdoor hack if that
    > >>helps!
    > >>
    > >
    > > If you're on x86 you can use collect rdtsc samples and convert them to ms.
    > > You'll get even more then ms accuracy.
    >
    >
    > Can I do this from user space? If so, any examples or docs
    > you can point me to?
    >
    > Also, I'm looking primarily for a speed increase, not an accuracy
    > increase.


    #include <linux/timex.h>


    unsigned long long mscurr;
    cycles_t cys, cye, mscycles;
    struct timespec ts1, ts2;

    clock_gettime(CLOCK_REALTIME, &ts1);
    cys = get_cycles();
    sleep(1);
    clock_gettime(CLOCK_REALTIME, &ts2);
    cye = get_cycles();
    mscycles = (cye - cys) / ((ts2.tv_sec - ts1.tv_sec) * 1000 +
    (ts2.tv_nsec - ts1.tv_nsec) / 1000000);



    mscurr = ts2.tv_sec * 1000 + ts2.tv_nsec * 1000000 + (get_cycles() - cye) / mscycles;





    - Davide


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