profil man page on FreeBSD

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PROFIL(2)		    BSD 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 profiling
     clock tick, the kernel updates an appropriate count in the samples buf‐
     fer.  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 pro‐
     gram 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 intermediate
     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() function appeared in Version 7 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.

BSD				 June 4, 1993				   BSD
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