Mtime gives access to the 64-bit free running system timer
counter. Note that this time is independent from the CPU speed.
val elapsed_us :
unit -> span_us
elapsed ()is the number of microseconds elasped since boot time.
val sleep_us :
span_us -> unit
sleep_us dblocks and sleeps for
val counter :
unit -> counter
counter ()is a counter counting from call time on.
val counter_value_us :
counter -> span_us
counter_value_us cis the current counter value in microseconds.
val s_to_us :
s_to_usis the number of microseconds in one second.
val ms_to_us :
ms_to_usis the number of microseconds in one millisecond.