gprof(1)

NAME

gprof — display call graph profile data

SYNOPSIS

gprof [options] [a.out [gmon.out...]]

DESCRIPTION

The gprof command produces an execution profile of C++, C and FORTRAN programs. The effect of called routines is incorporated into the profile of each caller. Profile data is taken from the call graph profile file (gmon.out default) that is created by programs compiled with the -G option of aCC, cc, and f90 and linked with libgprof.so or libgprof.sl, for IA and PA, respectively. The -G option also links in versions of the library routines that are compiled for profiling.

gprof(1) supports profiling of multiple shared libraries.

The symbol table for the load modules being profiled are read and correlated with the call graph profile file (gmon.out). To have the full call graph, no load module symbol table may be chopped; that is, no compiles may use the -x option. If more than one profile file is specified, gprof output shows the sum of the profile information in the given profile files.

First, a flat profile is given, similar to that provided by prof (see prof(1)). This listing gives the total execution times and call counts for each function in the load modules being profiled, sorted by decreasing time. The module index is also reported for each function signifying the load module in which the function is defined.

Next, these times are propagated along the edges of the call graph. gprof discovers all cycles in the call graph. All calls made into the cycle share the time of that cycle. A second listing shows the functions sorted according to the time they represent including the time of their call graph descendants. Below each function entry is shown its (direct) call graph children, and how their times are propagated to this function. A similar display above the function shows how the time of this function and the time of its descendants are propagated to its (direct) call graph parents.

Cycles are also shown, with an entry for the cycle as a whole and a listing of the members of the cycle, each with their contributions to the time and call counts of the cycle.

In the end a mapping of all module indices to module names is given. The modules not being profiled are reported at the top of output.

Shared Library Profiling

Support for gprof-style profiling of shared libraries is available both on 32-bit and 64-bit systems.

The environment variable LD_PROFILE determines what load modules get profiled; the environment variable LD_PROFILEBUCKET_SIZE controls the size of profiling counters. See the section below, Environment Variables.

At program termination the gprof library dumps all profiling information on a per-module basis in gmon.out, which the gprof command reads and matches to corresponding functions in the load modules.

Options

The gprof command recognizes the following options:

-a: Suppress printing statically declared functions. If this option is given, all relevant information about the static function (such as time samples, calls to other functions, and calls from other functions) belongs to the function loaded just before the static function in the a.out file.
-b: Suppress printing a description of each field in the profile.
-e name: Suppress printing the graph profile entry for routine name and all its descendants (unless they have other ancestors that are not suppressed). More than one -e option can be given. Only one name can be given with each -e option.
-E name: Suppress printing the graph profile entry for routine name (and its descendants) as -e above, and also exclude the time spent in name (and its descendants) from the total and percentage time computations. -E mcount -E mcleanup is the default.
-f name: Print only the graph profile entry of the specified routine name and its descendants. More than one -f option can be given. Only one name can be given with each -f option.
-F name: Print only the graph profile entry of the routine name and its descendants (as -f above) and also use only the times of the printed routines in total time and percentage computations. More than one -F option can be given. Only one name can be given with each -F option. The -F option overrides the -E option.
-p: Produce just the flat profile output exactly similar to one given by prof (see prof(1)).
-s: Produce a profile file gmon.sum that represents the sum of the profile information in all specified profile files. This summary profile file can be given to subsequent executions of gprof (probably also with a -s option) to accumulate profile data across several runs of an a.out file. LD_PROFILE should be set to the same string for all the runs.
-t: Produce just the static output in gprof. This is used for testing purposes. It eliminates all the timing information from normal gprof output and reports only the call count part.
-z: Display routines that have zero usage (as indicated by call counts and accumulated time).

EXTERNAL INFLUENCES

Environment Variables

LD_PROFILE determines the modules to be profiled as follows.

LD_PROFILE=ALL: Profile all load modules. That is, report timing and call count information for all loadable modules, including a.out.
LD_PROFILE=ldm1:ldm2: Profile only loadable modules ldm1 and ldm2. ldm1 and ldm2 are not full pathnames; they are the names recorded in the executables, which can be displayed using chatr(1).

On IA, if LD_PROFILE is not set, gprof behaves as though LD_PROFILE=ALL. On PA, LD_PROFILE has to be set for any profiling to occur.

LD_PROFILEBUCKET_SIZE controls the size of profiling counters. The acceptable value for this variable is 16 or 32. Counter size can also be specified at compile time using the +profilebucketsize option. The runtime value overrides the compile time value. A warning is issued if the counter size is set to a value other than 16 or 32; in this case the value specified at compile time is used. The default value of the counter is 16, which is used if a valid value is not specified. See the description of the cc(1) +profilebucketsize option for more details.

GPROFDIR controls the name of the file created by a profiled program. If GPROFDIR is not set, gmon.out is produced in the current directory when the program terminates. If GPROFDIR=string, string/pid.progname is produced, where progname is argv[0] with any path prefix removed, and pid is the program's process ID. If GPROFDIR is set to a null string, no profiling output is produced.

EXAMPLES

To profile a.out and libtest.so on IA. PA profiling is also done in the same way.

$ cat > test.c
void a()
{
        printf("I in a\n");
}

$ cc -c +Z -G test.c
$ ld -b -o libtest.so.1 test.o
$ ln -s ./libtest.so.1 libtest.so

$ cat main.c
extern void a();
main()
{
        printf("Hello world\n");
        a();
}

$ cc -G main.c  -L. -ltest
$ export LD_PROFILE=a.out:libtest.so
$ export LD_PROFILEBUCKET_SIZE=16

$ ./a.out
hello world
I in a

$ unset LD_PROFILE
$ unset LD_PROFILEBUCKET_SIZE
$ ls gmon.out
gmon.out
$ gprof

WARNINGS

Beware of quantization errors. The granularity of the sampling is shown, but remains statistical at best. It is assumed that the time for each execution of a function can be expressed by the total time for the function, divided by the number of times the function is called. Thus the time propagated along the call graph arcs to parents of that function is directly proportional to the number of times that arc is traversed.

Parents that are not profiled have the time of their profiled children propagated to them, but they appear to be spontaneously invoked in the call graph listing, and do not have their time propagated further. Similarly, signal catchers, even though profiled, appear to be spontaneous (although for more obscure reasons). Any profiled children of signal catchers should have their times propagated properly unless the signal catcher was invoked during the execution of the profiling routine, in which case all is lost.

DEPENDENCIES

gprof cannot be used with dynamically linked executables (built with ld -A in pre-HP-UX 10.20 releases).

AUTHOR

gprof was developed by the University of California, Berkeley.

FILES

a.out*: Default object file.
gmon.out*: Default dynamic call graph and profile.
gmon.sum*: Summarized dynamic call graph and profile.
/usr/lib/gprof.callg*: Call graph description.
/usr/lib/gprof.flat*: Flat profile description.
/usr/lib/hpux32/libgprof.so: gprof 32-bit shared library profiler on IA.
/usr/lib/hpux64/libgprof.so: gprof 64-bit shared library profiler on IA.
/usr/lib/libgprof.sl: gprof 32-bit shared library profiler on PA.
/usr/lib/pa20_64/libgprof.sl: gprof 64-bit shared library profiler on PA.