xenial (3) __ppc_get_timebase_freq.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.

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.

VERSIONS

       GNU  C  Library  support  for  __ppc_get_timebase()  has   been   provided   since   version   2.16   and
       __ppc_get_timebase_freq() has been available since version 2.17.

CONFORMING TO

       Both functions are nonstandard GNU extensions.

EXAMPLE

       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 = __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)

COLOPHON

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