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.TH __PPC_GET_TIMEBASE 3 2017-09-15 "GNU C Library" "Linux Programmer's\

Manual"

.SH NAME

__ppc_get_timebase, __ppc_get_timebase_freq \- get the current value

 of the Time Base Register on Power architecture and its frequency.

.SH SYNOPSIS

.B #include <sys/platform/ppc.h>

.PP

.BI "uint64_t __ppc_get_timebase(void)"

.PP

.BI "uint64_t __ppc_get_timebase_freq(void);"

.SH DESCRIPTION

.BR __ppc_get_timebase ()

reads the current value of the Time Base Register and returns its

value, while

.BR __ppc_get_timebase_freq ()

returns the frequency in which the Time Base Register is updated.

.PP

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.

.SH RETURN VALUE

.BR __ppc_get_timebase ()

returns a 64-bit unsigned integer that represents the current value of the

Time Base Register.

.PP

.BR __ppc_get_timebase_freq ()

returns a 64-bit unsigned integer that represents the frequency at

which the Time Base Register is updated.

.SH VERSIONS

GNU C Library support for

.\" commit d9dc34cd569bcfe714fe8c708e58c028106e8b2e

.BR __ppc_get_timebase ()

has been provided since version 2.16 and

.\" commit 8ad11b9a9cf1de82bd7771306b42070b91417c11

.BR __ppc_get_timebase_freq ()

has been available since version 2.17.

.SH CONFORMING TO

Both functions are nonstandard GNU extensions.

.SH EXAMPLE

The following program will calculate the time, in microseconds, spent

between two calls to

.BR __ppc_get_timebase ().

.SS Program source

\&

.EX

#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);

}

.EE

.SH SEE ALSO

.BR time (2),

.BR usleep (3)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I 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/.