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().

#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)