Tribblix: manual page: monitor.3c

MONITOR(3C) Standard C Library Functions MONITOR(3C)

NAME

monitor - prepare process execution profile

SYNOPSIS

#include <mon.h>

void monitor(int (*lowpc(), int (*highpc)(), WORD *buffer, size_t bufsize,
size_t nfunc);

DESCRIPTION

The monitor() function is an interface to the profil(2) function and
is called automatically with default parameters by any program
created by the cc utility with the -p option specified. Except to
establish further control over profiling activity, it is not
necessary to explicitly call monitor().

When used, monitor() is called at least at the beginning and the end
of a program. The first call to monitor() initiates the recording of
two different kinds of execution-profile information: execution-time
distribution and function call count. Execution-time distribution
data is generated by profil() and the function call counts are
generated by code supplied to the object file (or files) by cc -p.
Both types of information are collected as a program executes. The
last call to monitor() writes this collected data to the output file
mon.out.

The name of the file written by monitor() is controlled by the
environment variable PROFDIR. If PROFDIR does not exist, the file
mon.out is created in the current directory. If PROFDIR exists but
has no value, monitor() does no profiling and creates no output file.
If PROFDIR is dirname, and monitor() is called automatically by
compilation with cc -p, the file created is dirname/pid.progname
where progname is the name of the program.

The lowpc and highpc arguments are the beginning and ending addresses
of the region to be profiled.

The buffer argument is the address of a user-supplied array of WORD
(defined in the header <mon.h>). The buffer argument is used by
monitor() to store the histogram generated by profil() and the call
counts.

The bufsize argument identifies the number of array elements in
buffer.

The nfunc argument is the number of call count cells that have been
reserved in buffer. Additional call count cells will be allocated
automatically as they are needed.

The bufsize argument should be computed using the following formula:

size_of_buffer =
sizeof(struct hdr) +
nfunc * sizeof(struct cnt) +
((highpc-lowpc)/BARSIZE) * sizeof(WORD) +
sizeof(WORD) - 1 ;
bufsize = (size_of_buffer / sizeof(WORD));

where:

o lowpc, highpc, nfunc are the same as the arguments to
monitor();

o BARSIZE is the number of program bytes that correspond to
each histogram bar, or cell, of the profil() buffer;

o the hdr and cnt structures and the type WORD are defined
in the header <mon.h>.

The default call to monitor() is as follows:

monitor (&eprol, &etext, wbuf, wbufsz, 600);

where:

o eprol is the beginning of the user's program when linked
with cc -p (see end(3C));

o etext is the end of the user's program (see end(3C));

o wbuf is an array of WORD with wbufsz elements;

o wbufsz is computed using the bufsize formula shown above
with BARSIZE of 8;

o 600 is the number of call count cells that have been
reserved in buffer.

These parameter settings establish the computation of an execution-
time distribution histogram that uses profil() for the entire
program, initially reserves room for 600 call count cells in buffer,
and provides for enough histogram cells to generate significant
distribution-measurement results. For more information on the effects
of bufsize on execution-distribution measurements, see profil(2).

EXAMPLES

Example 1: Example to stop execution monitoring and write the results

to a file.

To stop execution monitoring and write the results to a file, use the
following:

monitor((int (*)())0, (int (*)())0, (WORD *)0, 0, 0);

Use prof to examine the results.

USAGE

Additional calls to monitor() after main() has been called and before
exit() has been called will add to the function-call count capacity,
but such calls will also replace and restart the profil() histogram
computation.

ATTRIBUTES