__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);
}
This page is part of release 4.07 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
https://www.kernel.org/doc/man−pages/.
|
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 and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume. no responsibility for errors or omissions, or for damages resulting. from the use of the information contained herein. The author(s) may. not have taken the same level of care in the production of this. manual, which is licensed free of charge, as they might when working. professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |