__ppc_get_timebase (3)

Leading comments

Copyright (c) 2012, IBM Corporation.

%%%LICENSE_START(VERBATIM)
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that
the entire resulting derived work is distributed under the terms of
a permission notice identical to this one.

Since the Linux kernel...

(The comments found at the beginning of the groff file "man3/__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.

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 4.04 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 www.kernel.org/doc/man-pages