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PROFIL(2)		      System Calls Manual		     PROFIL(2)

NAME
       profil -- control process profiling

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<unistd.h>

       int
       profil(char *samples, size_t size, vm_offset_t offset, int scale);

DESCRIPTION
       The  profil() system call enables or disables program counter profiling
       of the current process.	If profiling is	enabled, then at every profil-
       ing clock tick, the kernel updates an appropriate count in the  samples
       buffer.	The frequency of the profiling clock is	recorded in the	header
       in the profiling	output file.

       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 profiling 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  argument  is  the lowest address at	which the kernel takes
       program counter samples.	 The scale argument 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 in-
       termediate ranges.  A scale value of 0 disables profiling.

RETURN VALUES
       The profil() function returns the value 0 if successful;	otherwise  the
       value  -1  is returned and the global variable errno is set to indicate
       the error.

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

ERRORS
       The following error may be reported:

       [EFAULT]		  The buffer samples contains an invalid address.

SEE ALSO
       gprof(1)

HISTORY
       The profil() functionality first	appeared in Version 3 AT&T UNIX.

BUGS
       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.

FreeBSD	13.2		       December	1, 2017			     PROFIL(2)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | FILES | ERRORS | SEE ALSO | HISTORY | BUGS

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