__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)
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14       uint64_t __ppc_get_timebase_freq(void);
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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.
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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.
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RETURN VALUE

27       __ppc_get_timebase() returns a 64-bit unsigned integer that  represents
28       the current value of the Time Base Register.
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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.
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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.
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CONFORMING TO

39       Both functions are nonstandard GNU extensions.
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EXAMPLE

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

88       This  page  is  part of release 5.02 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/.
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95GNU C Library                     2019-03-06             __PPC_GET_TIMEBASE(3)