VTIME_PER_SEC
VTIME_PER_USEC = VTIME_PER_SEC / USEC_PER_SEC,
VTIME_PER_NSEC = VTIME_PER_SEC / NSEC_PER_SEC,
*page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, bps_pages);
v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops);
v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops);