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().

#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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