__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 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.

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 = __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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