MONITOR(3)MONITOR(3)NAME
monitor, monstartup, moncontrol, moninit, monreset, monoutput,
monaddition, moncount - prepare execution profile
SYNOPSIS
extern void monstartup(
char *lowpc,
char *highpc);
extern void monitor(
char *lowpc,
char *highpc,
char *buf,
int bufsiz,
int nfunc);
extern void moncontrol(
int mode);
extern void moninit(void);
extern void moninitshlibs(void);
extern void monreset(void);
extern void monoutput(
const char *filename);
extern void monaddition(
char *lowpc,
char *highpc);
extern void moncount(
char *frompc,
char *selfpc)
DESCRIPTION
These functions support execution profiling. An executable program
created with the profiling option -pg of cc(1) automatically includes
calls for the gprof(1) monitor, which displays execution times and
statistics for the functions in the program. The functions described
here provide different sorts of control over the profiling.
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 a buffer and passes it to monitor (see below),
which records into it a histogram of periodically sampled values of the
program counter, as well as counts of calls to certain functions. Only
calls to functions compiled with the profiling option -pg of cc(1) are
recorded.
To profile the entire program, it is sufficient to include the line:
moninit();
in the source code. This routine is invoked just before main() is
called, if the program is linked with the profiling run-time start-off
(/lib/gcrt0.o). The profiling run-time start-off is used instead of
the standard run-time start-off when the program is linked with cc(1)
and the profiling option -pg is specified on the link line.
To stop execution monitoring and write the results on the file
gmon.out, use
monitor(0);
Again, this happens automatically in the profiling run-time startoff,
which defines a version of exit(2) that makes this call to monitor.
After the file gmon.out is written, the program gprof(1) can be used to
examine the results.
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);
and 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.
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. The parameter nfunc is
ignored and exists only for historical reasons. 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. The space to record call counts of functions compiled
with the -pg option to cc(1) is allocated by moncount.
Moninit is invoked just before main() is called in the profiling run-
time start-off (/lib/gcrt0.o). It sets up the entire program to be
profiled. This includes a call to moninitshlibs, which causes entry
points in any shared libraries used to have their call counts and
histogram ticks of the shared libraries' code to be recorded.
Recording for shared libraries can be disabled by linking in a version
of moninitshlibs that does nothing. Moninit also causes the Objective-
C run-time system to record counts for Objective-C messages that are
sent. Moninit also sets up profiling for any code that will be loaded
with rld(3). For call counts of the code loaded with rld(3) to be
recorded, the code must have been compiled with the profiling option
-pg of cc(1).
Monreset resets all the histogram ticks and call counts to zero.
Monoutput writes the profiling information into the specified output
file.
To the existing set of regions, monaddition adds a region to record
histogram ticks and call counts. This function is used to add regions
for shared libraries and code loaded with rld(3).
Moncount is the routine that increments the call counts for the call
site frompc which is calling the routine at selfpc. Moncount gets
called at the beginning of each routine compiled with the profiling
option -pg to cc(1).
FILES
gmon.out
SEE ALSOcc(1), gprof(1), profil(2)NeXT, Inc. July 29, 1993 MONITOR(3)
