__ppc_get_timebase_freq

__PPC_GET_TIMEBASE(3)      Linux Programmer'sManual      __PPC_GET_TIMEBASE(3)

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 fre-
       quency in which the Time Base Register is updated.

       The Time Base Register is a 64-bit register provided by Power Architec-
       ture 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 repre-
       sents 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
       This  page  is  part of release 5.05 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU C Library                     2019-03-06             __PPC_GET_TIMEBASE(3)