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   __ppc_get_timebase    ( 3 )

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Имя (Name)

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

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Синопсис (Synopsis)

#include <sys/platform/ppc.h>

uint64_t __ppc_get_timebase(void); uint64_t __ppc_get_timebase_freq(void);

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Описание (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.

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Возвращаемое значение (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.

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Версии (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.

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Стандарты (Conforming to)

Both functions are nonstandard GNU extensions.

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Примеры (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: 2^60 - 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);
       }

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Смотри также (See also)

time(2), usleep(3)

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