monitor(3) Library Functions Manual 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
These functions use the system call to control program-counter sampling. Using the option -p when compiling or linking a program automati-
cally generates calls to these functions. You do need not to call these functions explicitly unless you want more control.
Typically, you would call either or to initialize pc-sampling and enable it; call to disable or reenable it; and call at the end of execu-
tion to disable sampling and record the samples in a file.
Your initial call to enables pc-sampling. The parameters lowpc and highpc specify the range of addresses to be sampled. The lowest
address is that of lowpc and the highest is just below highpc. The buffer parameter is the address of a (user allocated) array of bufsize
short integers, which holds a record of the samples; for best results, the buffer should not be less than a few times smaller than the
range of addresses sampled. The nfunc parameter is ignored.
The environment variable PROFDIR determines the name of the output file and whether pc-sampling takes place: if it is not set, the file is
named mon.out; if set to the empty string, no pc-sampling occurs; if set to a non-empty string, the file is named string/pid.progname,
where pid is the process id of the executing program and progname is the program's name as it appears in argv[0]. The subdirectory string
must already exist.
To profile the entire program, use the following:
extern eprol(), etext();
. . .
monitor(eprol, etext, buf, bufsize, 0);
The routine lies just below the user program text, and lies just above it, as described in (Because the user program does not necessarily
start at a low memory address, using a small number in place of is dangerous).
The routine is an alternate form of that calls (see for you to allocate the buffer.
The function selectively disables and re-enables pc-sampling within a program, allowing you to measure the cost of particular operations.
The function disables pc-sampling, and reenables it.
To stop execution monitoring and write the results in the output file, use the following:
monitor(0);
Files
mon.out default name for output file
libprof1.a routines for pc-sampling
See Also
cc(1), ld(1), profil(2), brk(2)
RISC monitor(3)
