__ppc_get_timebase, __ppc_get_timebase_freq — get the current value of the Time Base Register on Power architecture and its frequency.
#include <sys/platform/ppc.h>
uint64_t
__ppc_get_timebase( |
void) uint64_t __ppc_get_timebase_freq(void); |
__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.
__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.
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.
The following program will calculate the time, in
microseconds, spent between two calls to __ppc_get_timebase().
#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);
}