pcsample(2)							   System Calls 						       pcsample(2)

NAME

       pcsample - program execution time profile

SYNOPSIS

       #include <pcsample.h>

       long pcsample(uintptr_t samples[], long nsamples);

DESCRIPTION

       The pcsample() function provides CPU-use statistics by profiling the amount of CPU time expended by a program.

       For profiling dynamically-linked programs and 64-bit programs, it is superior to the profil(2) function, which assumes that the entire pro-
       gram is contained in a small, contiguous segment of the address space, divides this segment into "bins", and on each clock tick	increments
       the  counter  in  the  bin  where  the program is currently executing. With shared libraries creating discontinuous program segments spread
       throughout the address space, and with 64-bit address spaces so large that the size of "bins" would be measured in megabytes, the  profil()
       function is of limited value.

       The pcsample() function is passed an array samples containing nsamples pointer-sized elements. During program execution, the kernel samples
       the program counter of the process, storing unadulterated values in the array on each clock tick. The kernel stops  writing  to	the  array
       when  it  is  full,  which  occurs  after  nsamples  /  HZ  seconds  of process virtual time. The HZ value is obtained by invoking the call
       sysconf(_SC_CLK_TCK). See sysconf(3C).

       The sampling can be stopped by a subsequent call to pcsample() with the nsamples argument set to  0.   Like  profil(),  sampling  continues
       across  a call to fork(2), but is disabled by a call to one of the exec family of functions (see exec(2)). It is also disabled if an update
       of the samples[] array causes a memory fault.

RETURN VALUES

       The pcsample() function always returns 0 the first time it is called.  On subsequent calls, it returns the  number  of  samples	that  were
       stored during the previous invocation. If nsamples is invalid, it returns -1 and sets errno to indicate the error.

ERRORS

       The pcsample() function will fail if:

       EINVAL	       The value of nsamples is not valid.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Stable			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       exec(2), fork(2), profil(2), sysconf(3C), attributes(5)

SunOS 5.10							    10 Mar 1998 						       pcsample(2)