Linux内核时间

static size_t print_time(u64 ts, char *buf)
{
    unsigned long rem_nsec;

    if (!printk_time)
        return 0;

    rem_nsec = do_div(ts, 1000000000); /*ts=ts/1000000000, rem_nsec是余数，单位是ns*/

    if (!buf)
        return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);

    return sprintf(buf, "[%5lu.%06lu] ", (unsigned long)ts, rem_nsec / 1000); /*这里显示的是秒.微妙*/
}