/*
 * __wt_clock --
 *     Obtain a timestamp via either a CPU register or via a system call on platforms where
 *     obtaining it directly from the hardware register is not supported.
 */
static WT_INLINE uint64_t
__wt_clock(WT_SESSION_IMPL *session)
{
    struct timespec tsp;

    /*
     * In one case we return nanoseconds, in the other we return clock ticks. That looks wrong, but
     * it's not. When simply comparing before and after values, which is returned doesn't matter.
     * When trying to calculate wall-clock time (that is, comparing a starting time with an ending
     * time), we'll subtract the two values and then call a function to convert the result of the
     * subtraction into nanoseconds. In the case where we already have nanoseconds, that function
     * has a conversion constant of 1 and we'll skip the conversion, in the case where we have clock
     * ticks, the conversion constant will be real. The reason is because doing it that way avoids a
     * floating-point operation per wall-clock time calculation.
     */
    if (__wt_process.use_epochtime) {
        __wt_epoch(session, &tsp);
        return ((uint64_t)(tsp.tv_sec * WT_BILLION + tsp.tv_nsec));
    }
    return (__wt_rdtsc());
}