gethrvtime(3C)

NAME

     gethrtime, gethrvtime - get high resolution time

SYNOPSIS

     #include <sys/time.h>

     hrtime_t gethrtime(void);

     hrtime_t gethrvtime(void);

DESCRIPTION

     The gethrtime() function returns the current high-resolution
     real time. Time is expressed as nanoseconds since some arbi-
     trary 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.

     The  gethrvtime()  function  returns   the   current   high-
     resolution  LWP virtual time, expressed as total nanoseconds
     of execution time. This function requires that  micro  state
     accounting be enabled with the ptime utility (see proc(1)).

     The gethrtime() and gethrvtime() functions  both  return  an
     hrtime_t, which is a 64-bit (long long) signed integer.

EXAMPLES

     The following code fragment measures  the  average  cost  of
     getpid(2):

     hrtime_t start, end;
     int i, iters = 100;

     start = gethrtime();
     for (i = 0; i < iters; i++)
             getpid();
     end = gethrtime();

     printf("Avg getpid() time = %lld nsec\n", (end - start) / iters);

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|

SEE ALSO

     proc(1),  adjtime(2),  gettimeofday(3C),   settimeofday(3C),
     attributes(5)

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 won't go back-
     ward, it won't periodically wrap) and linear (it won't occa-
     sionally speed up or slow down for adjustment, like the time
     of  day  can),  but not necessarily unique: two sufficiently
     proximate calls may return the same value.