__PPC_GET_TIMEBASE(3)					     Linux Programmer'sManual					     __PPC_GET_TIMEBASE(3)

NAME

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

SYNOPSIS

       #include <sys/platform/ppc.h>

       uint64_t __ppc_get_timebase(void)

       uint64_t __ppc_get_timebase_freq(void);

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.

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.

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.

CONFORMING TO

       Both functions are nonstandard GNU extensions.

EXAMPLE

       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
", 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
",
		   (double) diff * 1000000 / freq );

	   exit(EXIT_SUCCESS);
       }

SEE ALSO

       time(2), usleep(3)

GNU C Library							    2019-03-06						     __PPC_GET_TIMEBASE(3)