plucky (3) __ppc_get_timebase.3.gz

NAME

       __ppc_get_timebase,  __ppc_get_timebase_freq  -  get the current value of the Time Base Register on Power
       architecture and its frequency.

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/platform/ppc.h>

       uint64_t __ppc_get_timebase(void);
       uint64_t __ppc_get_timebase_freq(void);

DESCRIPTION

       __ppc_get_timebase() reads the current value of the Time Base  Register  and  returns  its  value,  while
       __ppc_get_timebase_freq() returns the frequency in which the Time Base Register is updated.

       The  Time  Base  Register  is  a  64-bit register provided by Power Architecture processors.  It stores a
       monotonically incremented value that is updated at a system-dependent frequency  that  may  be  different
       from the processor frequency.

RETURN VALUE

       __ppc_get_timebase() returns a 64-bit unsigned integer that represents the current value of the Time Base
       Register.

       __ppc_get_timebase_freq() returns a 64-bit unsigned integer that represents the frequency  at  which  the
       Time Base Register is updated.

STANDARDS

       GNU.

HISTORY

       __ppc_get_timebase()
              glibc 2.16.

       __ppc_get_timebase_freq()
              glibc 2.17.

EXAMPLES

       The   following   program  will  calculate  the  time,  in  microseconds,  spent  between  two  calls  to
       __ppc_get_timebase().

   Program source

       #include <inttypes.h>
       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/platform/ppc.h>

       /* Maximum value of the Time Base Register: 2^60 - 1.
          Source: POWER ISA.  */
       #define MAX_TB 0xFFFFFFFFFFFFFFF

       int
       main(void)
       {
           uint64_t tb1, tb2, diff;
           uint64_t freq;

           freq = __ppc_get_timebase_freq();
           printf("Time Base frequency = %"PRIu64" Hz\n", freq);

           tb1 = __ppc_get_timebase();

           // Do some stuff...

           tb2 = __ppc_get_timebase();

           if (tb2 > tb1) {
               diff = tb2 - tb1;
           } else {
               /* Treat Time Base Register overflow.  */
               diff = (MAX_TB - tb2) + tb1;
           }

           printf("Elapsed time  = %1.2f usecs\n",
                  (double) diff * 1000000 / freq);

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       time(2), usleep(3)