FreeBSD 7.0 manual page repository

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profil - control process profiling

 

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
      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 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.
      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.
      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.
 

Sections

Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.