Kernel Developer's Manual
NAME tvtohz — convert time interval to tick count
SYNOPSIS #include <sys/time.h>
tvtohz(struct timeval *tv);
DESCRIPTION The tvtohz() function accepts a single argument tv which specifies the time interval over which to calculate the number of system ticks that would elapse.
RETURN VALUES Returns the integral number of system ticks expected to elapse in the given interval, including the current tick.
function first appeared in FreeBSD 3.0
and was ported to NetBSD 4.0
as a part of timecounter(9)