__ppc_get_timebase(3)

1__PPC_GET_TIMEBASE(3)      Linux Programmer'sManual      __PPC_GET_TIMEBASE(3)
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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.
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SYNOPSIS

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

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

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

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

38       Both functions are nonstandard GNU extensions.
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EXAMPLES

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

87       This  page  is  part of release 5.12 of the Linux man-pages project.  A
88       description of the project, information about reporting bugs,  and  the
89       latest     version     of     this    page,    can    be    found    at
90       https://www.kernel.org/doc/man-pages/.
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94GNU C Library                     2021-03-22             __PPC_GET_TIMEBASE(3)