MONITOR(3)

NAME
monitor, monstartup, moncontrol - prepare execution profile

SYNOPSIS
monitor(lowpc, highpc, buffer, bufsize, nfunc)
int (*lowpc)(), (*highpc)();
short buffer[];

monstartup(lowpc, highpc)
int (*lowpc)(), (*highpc)();

moncontrol(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.

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 (see below) 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);

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

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

    monitor(0);

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

Moncontrol is used to selectively control profiling within a program. This works with either prof(1) or gprof(1) type profiling. 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 irregardless of the state of moncontrol.

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 short integers. At most nfunc call counts can be kept. 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. Monitor divides the buffer into space to record the histogram of program counter samples over the range lowpc to highpc, and space to record call counts of functions compiled with the -p option to cc(1).

To profile the entire program, it is sufficient to use

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

FILES
mon.out

SEE ALSO
cc(1), prof(1), gprof(1), profil(2), sbrk(2)