clockrequest_advance
count = clockrequest_advance(cr, dp->dp_nsecs);
count = clockrequest_advance(cr, statclock_avg);
count = clockrequest_advance(cr, hardclock_period);
nsecs = clockrequest_advance(cr, hardclock_period) * hardclock_period;
count = clockrequest_advance(cr, roundrobin_period);
count = clockrequest_advance(cr, profclock_period);
count = clockrequest_advance(cr, profclock_period);
uint64_t clockrequest_advance(struct clockrequest *, uint64_t);