monitor(3C)

NAME

monitor, monstartup, moncontrol − prepare execution profile

SYNOPSIS

#include <mon.h>

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

SYNOPSIS (4.2BSD)

void monstartup (lowpc, highpc)
int (∗lowpc)(), (∗highpc)();
void moncontrol (mode)
int mode;

DESCRIPTION

There are two different forms of monitoring available: An executable program created by:
cc −p . . .

automatically includes calls for the prof(1) monitor and includes an initial call to its start-up routine monstartup with default parameters; monitor need not be called explicitly except to gain fine control over profil buffer allocation. An executable program created by:
cc −pG. . .

automatically includes calls for the gprof(1) monitor.

monitor is a low-level interface to profil(2). Lowpc and highpc are the addresses of two functions; buffer is the address of a (user supplied) array of bufsize WORDs (defined in the <mon.h> header file). monitor arranges to record a histogram of periodically sampled values of the program counter, and of counts of calls of certain functions, in the buffer. The lowest address sampled is that of lowpc and the highest is just below highpc. Lowpc may not equal 0 for this use of monitor. At most nfunc call counts can be kept; only calls of functions compiled with the profiling option −p of cc(1) are recorded.

For the results to be significant, especially where there are small, heavily used routines, it is suggested that the buffer be no more than a few times smaller than the range of locations sampled.

To profile the entire program, it is sufficient to use

extern etext;
...
monitor ((int (∗)())2, etext, buf, bufsize, nfunc);

Etext lies just above all the program text; see end(3C).

To stop execution monitoring and write the results on the file mon.out, use

monitor ((int (∗)())0, 0, 0, 0, 0);

Prof(1) can then be used to examine the results.

Monstartup is a high-level interface to profil(2). Lowpc and highpc specify the address range that is to be sampled; the lowest address sampled is that of lowpc and the highest is just below highpc. Monstartup allocates space using sbrk(2) and passes it to monitor to record a histogram of periodically sampled values of the program counter, and of counts of calls of certain functions, in the buffer. Only calls of functions compiled with the profiling option −p of cc(1) are recorded.

To profile the entire program, it is sufficient to use

extern etext();
. . .
monstartup((int) 2, etext);

Moncontrol is used to selectively control profiling within a program. When the program starts, profiling begins. To stop the collection of histogram ticks and call counts use moncontrol(0); to resume the collection of histogram ticks and call counts use moncontrol(1). This allows the cost of particular operations to be measured. Note that an output file will be produced upon program exit regardless of the state of moncontrol.

NOTE

The format of a profile file is not guaranteed to be portable across systems provided by different vendors. In particular, Motorola 88000 programs which are certified to conform to the 88open Compatibility Standards may not be profilable on a foreign system.

FILES

mon.out
/lib/libp/libc.a
/lib/libp/libm.a

Museum

Related Articles