man3/__ppc_get_timebase.3

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  25 .TH __PPC_GET_TIMEBASE 3 2015-07-23 "GNU C Library" "Linux Programmer's\
  26 Manual"
  27 .SH NAME
  28 __ppc_get_timebase, __ppc_get_timebase_freq \- get the current value
  29  of the Time Base Register on Power architecture and its frequency.
  30 .SH SYNOPSIS
  31 .B #include <sys/platform/ppc.h>
  32 .PP
  33 .BI "uint64_t __ppc_get_timebase(void)"
  34 .PP
  35 .BI "uint64_t __ppc_get_timebase_freq(void);"
  36 .SH DESCRIPTION
  37 .BR __ppc_get_timebase ()
  38 reads the current value of the Time Base Register and returns its
  39 value, while
  40 .BR __ppc_get_timebase_freq ()
  41 returns the frequency in which the Time Base Register is updated.
  42 .PP
  43 The Time Base Register is a 64-bit register provided by Power Architecture
  44 processors.
  45 It stores a monotonically incremented value that is updated at a
  46 system-dependent frequency that may be different from the processor
  47 frequency.
  48 .SH RETURN VALUE
  49 .BR __ppc_get_timebase ()
  50 returns a 64-bit unsigned integer that represents the current value of the
  51 Time Base Register.
  52 .PP
  53 .BR __ppc_get_timebase_freq ()
  54 returns a 64-bit unsigned integer that represents the frequency at
  55 which the Time Base Register is updated.
  56 .SH VERSIONS
  57 GNU C Library support for
  58 .\" commit d9dc34cd569bcfe714fe8c708e58c028106e8b2e
  59 .BR __ppc_get_timebase ()
  60 has been provided since version 2.16 and
  61 .\" commit 8ad11b9a9cf1de82bd7771306b42070b91417c11
  62 .BR __ppc_get_timebase_freq ()
  63 has been available since version 2.17.
  64 .SH CONFORMING TO
  65 Both functions are nonstandard GNU extensions.
  66 .SH EXAMPLE
  67 The following program will calculate the time, in microseconds, spent
  68 between two calls to
  69 .BR __ppc_get_timebase ().
  70 .SS Program source
  71 \&
  72 .nf
  73 #include <inttypes.h>
  74 #include <stdint.h>
  75 #include <stdio.h>
  76 #include <stdlib.h>
  77 #include <sys/platform/ppc.h>
  78
  79 /* Maximum value of the Time Base Register: 2^60 \- 1.
  80    Source: POWER ISA.  */
  81 #define MAX_TB 0xFFFFFFFFFFFFFFF
  82
  83 int
  84 main(void)
  85 {
  86     uint64_t tb1, tb2, diff;
  87
  88     uint64_t freq = __ppc_get_timebase_freq();
  89     printf("Time Base frequency = %"PRIu64" Hz\\n", freq);
  90
  91     tb1 = __ppc_get_timebase();
  92
  93     // Do some stuff...
  94
  95     tb2 = __ppc_get_timebase();
  96
  97     if (tb2 > tb1) {
  98         diff = tb2 \- tb1;
  99     } else {
 100         /* Treat Time Base Register overflow.  */
 101         diff = (MAX_TB \- tb2) + tb1;
 102     }
 103
 104     printf("Elapsed time  = %1.2f usecs\\n",
 105             (double) diff * 1000000 / freq );
 106
 107     exit(EXIT_SUCCESS);
 108 }
 109 .fi
 110 .SH SEE ALSO
 111 .BR time (2),
 112 .BR usleep (3)