GETHRTIME(9F) Kernel Functions for Drivers GETHRTIME(9F)

NAME

gethrtime - get high resolution time

SYNOPSIS

#include <sys/time.h>


hrtime_t gethrtime(void);

DESCRIPTION

The gethrtime() function returns the current high-resolution real
time. Time is expressed as nanoseconds since some arbitrary time in
the past; it is not correlated in any way to the time of day, and
thus is not subject to resetting or drifting by way of adjtime(2) or
settimeofday(3C). The hi-res timer is ideally suited to performance
measurement tasks, where cheap, accurate interval timing is required.

RETURN VALUES

gethrtime() always returns the current high-resolution real time.
There are no error conditions.

CONTEXT

There are no restrictions on the context from which gethrtime() can
be called.

SEE ALSO

proc(1), gettimeofday(3C), settimeofday(3C), attributes(7)

NOTES

Although the units of hi-res time are always the same (nanoseconds),
the actual resolution is hardware dependent. Hi-res time is
guaranteed to be monotonic (it does not go backward, it does not
periodically wrap) and linear (it does not occasionally speed up or
slow down for adjustment, as the time of day can), but not
necessarily unique: two sufficiently proximate calls might return the
same value.


The time base used for this function is the same as that for
gethrtime(3C). Values returned by both of these functions can be
interleaved for comparison purposes.

October 2, 2007 GETHRTIME(9F)