functions store the time elapsed since boot as a
Vt struct bintime
at the address specified by
Fa bt .
functions perform the same utility, but record the elapsed time as a
Vt struct timeval
functions store the elapsed time as a
Vt struct timespec .
always query the timecounter to return the current time as precisely as
functions are abstractions which return a less precise, but
faster to obtain, time.
The intent of the
functions is to enforce the user's preference for timer accuracy versus