Man page - __ppc_get_timebase_freq(3)

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__ppc_get_timebase

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
STANDARDS
HISTORY
EXAMPLES
Program source
SEE ALSO

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 ().

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;
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);
}