NAME    [Toc]    [Back]

     profil - control process profiling

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>

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

DESCRIPTION    [Toc]    [Back]

     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 samples.  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.

RETURN VALUES    [Toc]    [Back]

     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.

FILES    [Toc]    [Back]

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

ERRORS    [Toc]    [Back]

     The following error may be reported:

     [EFAULT]      The buffer samples  contains  an  invalid  address.

SEE ALSO    [Toc]    [Back]

     gprof(1)

BUGS    [Toc]    [Back]

     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.

OpenBSD      3.6                           June      4,      1993