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__PPC_GET_TIMEBASE(3) Linux Programmer'sManual __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)
GNU C Library 2021-03-22 __PPC_GET_TIMEBASE(3)