__ppc_get_timebase(3)

1__PPC_GET_TIMEBASE(3)      Linux Programmer'sManual      __PPC_GET_TIMEBASE(3)
2
3
4

NAME

6       __ppc_get_timebase, __ppc_get_timebase_freq - get the current value
7        of the Time Base Register on Power architecture and its frequency.
8

SYNOPSIS

10       #include <sys/platform/ppc.h>
11
12       uint64_t __ppc_get_timebase(void)
13
14       uint64_t __ppc_get_timebase_freq(void);
15

DESCRIPTION

17       __ppc_get_timebase()  reads the current value of the Time Base Register
18       and returns its value, while __ppc_get_timebase_freq() returns the fre‐
19       quency in which the Time Base Register is updated.
20
21       The Time Base Register is a 64-bit register provided by Power Architec‐
22       ture processors.  It stores a monotonically incremented value  that  is
23       updated  at a system-dependent frequency that may be different from the
24       processor frequency.
25

RETURN VALUE

27       __ppc_get_timebase() returns a 64-bit unsigned integer that  represents
28       the current value of the Time Base Register.
29
30       __ppc_get_timebase_freq() returns a 64-bit unsigned integer that repre‐
31       sents the frequency at which the Time Base Register is updated.
32

VERSIONS

34       GNU C Library support for __ppc_get_timebase() has been provided  since
35       version  2.16  and  __ppc_get_timebase_freq()  has been available since
36       version 2.17.
37

CONFORMING TO

39       Both functions are nonstandard GNU extensions.
40

EXAMPLE

42       The following program will calculate the time, in  microseconds,  spent
43       between two calls to __ppc_get_timebase().
44
45   Program source
46
47       #include <inttypes.h>
48       #include <stdint.h>
49       #include <stdio.h>
50       #include <stdlib.h>
51       #include <sys/platform/ppc.h>
52
53       /* Maximum value of the Time Base Register: 2^60 - 1.
54          Source: POWER ISA.  */
55       #define MAX_TB 0xFFFFFFFFFFFFFFF
56
57       int
58       main(void)
59       {
60           uint64_t tb1, tb2, diff;
61
62           uint64_t freq = __ppc_get_timebase_freq();
63           printf("Time Base frequency = %"PRIu64" Hz\n", freq);
64
65           tb1 = __ppc_get_timebase();
66
67           // Do some stuff...
68
69           tb2 = __ppc_get_timebase();
70
71           if (tb2 > tb1) {
72               diff = tb2 - tb1;
73           } else {
74               /* Treat Time Base Register overflow.  */
75               diff = (MAX_TB - tb2) + tb1;
76           }
77
78           printf("Elapsed time  = %1.2f usecs\n",
79                   (double) diff * 1000000 / freq );
80
81           exit(EXIT_SUCCESS);
82       }
83

COLOPHON

88       This  page  is  part of release 4.15 of the Linux man-pages project.  A
89       description of the project, information about reporting bugs,  and  the
90       latest     version     of     this    page,    can    be    found    at
91       https://www.kernel.org/doc/man-pages/.
92
93
94
95GNU C Library                     2017-09-15             __PPC_GET_TIMEBASE(3)