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OpenDarwin 7.2.1 - man page for profil (opendarwin section 2)

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PROFIL(2)			     BSD System Calls Manual				PROFIL(2)

     profil -- control process profiling

     profil(char *samples, size_t size, u_long offset, u_int scale);

     The profil() function enables or disables program counter profiling of the current process.
     If profiling is enabled, then at every clock tick, the kernel updates an appropriate count
     in the samples buffer.

     The buffer samples contains size bytes and is divided into a series of 16-bit bins.  Each
     bin counts the number of times the program counter was in a particular address range in the
     process when a clock tick occurred while profiling was enabled.  For a given program counter
     address, the number of the corresponding bin is given by the relation:

	   [(pc - offset) / 2] * scale / 65536

     The offset parameter is the lowest address at which the kernel takes program counter sam-
     ples.  The scale parameter ranges from 1 to 65536 and can be used to change the span of the
     bins.  A scale of 65536 maps each bin to 2 bytes of address range; a scale of 32768 gives 4
     bytes, 16384 gives 8 bytes and so on.  Intermediate values provide approximate intermediate
     ranges.  A scale value of 0 disables profiling.

     If the scale value is nonzero and the buffer samples contains an illegal address, profil()
     returns -1, profiling is terminated and errno is set appropriately.  Otherwise profil()
     returns 0.

     /usr/lib/gcrt0.o  profiling C run-time startup file
     gmon.out	       conventional name for profiling output file

     The following error may be reported:

     [EFAULT]		The buffer samples contains an invalid address.


     This routine should be named profile().

     The samples argument should really be a vector of type unsigned short.

     The format of the gmon.out file is undocumented.

BSD					   June 4, 1993 				      BSD
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