__PPC_GET_TIMEBASE
Section: Linux Programmer'sManual (3)
Updated: 2021-03-22
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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: 2ha60 - 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)
COLOPHON
This page is part of release 5.11 of the Linux
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A description of the project,
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and the latest version of this page,
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Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- VERSIONS
-
- CONFORMING TO
-
- EXAMPLES
-
- Program source
-
- SEE ALSO
-
- COLOPHON
-
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Time: 06:22:45 GMT, May 09, 2021