gprof(1) User Commands gprof(1)NAMEgprof - display call-graph profile data
SYNOPSISgprof [-abcCDlsz] [-e function-name] [-E function-name]
[-f function-name] [-F function-name]
[image-file [profile-file...]]
[-n number of functions]
DESCRIPTION
The gprof utility produces an execution profile of a program. The
effect of called routines is incorporated in the profile of each call‐
er. The profile data is taken from the call graph profile file that is
created by programs compiled with the -xpg option of cc(1), or by the
-pg option with other compilers, or by setting the LD_PROFILE environ‐
ment variable for shared objects. See ld.so.1(1). These compiler
options also link in versions of the library routines which are com‐
piled for profiling. The symbol table in the executable image file
image-file (a.out by default) is read and correlated with the call
graph profile file profile-file (gmon.out by default).
First, execution times for each routine are propagated along the edges
of the call graph. Cycles are discovered, and calls into a cycle are
made to share the time of the cycle. The first listing shows the func‐
tions 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 this
function's time 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 and their contributions to the time
and call counts of the cycle.
Next, a flat profile is given, similar to that provided by prof(1).
This listing gives the total execution times and call counts for each
of the functions in the program, sorted by decreasing time. Finally, an
index is given, which shows the correspondence between function names
and call-graph profile index numbers.
A single function may be split into subfunctions for profiling by means
of the MARK macro. See prof(5).
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.
The profiled program must call exit(2) or return normally for the pro‐
filing information to be saved in the gmon.out file.
OPTIONS
The following options are supported:
-a Suppress printing statically declared functions. If
this option is given, all relevant information about
the static function (for instance, time samples,
calls to other functions, calls from other func‐
tions) belongs to the function loaded just before
the static function in the a.out file.
-b Brief. Suppress descriptions of each field in the
profile.
-c Discover the static call-graph of the program by a
heuristic which examines the text space of the
object file. Static-only parents or children are
indicated with call counts of 0. Note that for
dynamically linked executables, the linked shared
objects' text segments are not examined.
-C Demangle C++ symbol names before printing them out.
-D Produce a profile file gmon.sum that represents the
difference of the profile information in all speci‐
fied profile files. This summary profile file may
be given to subsequent executions of gprof (also
with -D) to summarize profile data across several
runs of an a.out file. See also the -s option.
As an example, suppose function A calls function B
n times in profile file gmon.sum, and m times in
profile file gmon.out. With -D, a new gmon.sum file
will be created showing the number of calls from A
to B as n-m.
-efunction-name Suppress printing the graph profile entry for rou‐
tine function-name and all its descendants (unless
they have other ancestors that are not suppressed).
More than one -e option may be given. Only one
function-name may be given with each -e option.
-Efunction-name Suppress printing the graph profile entry for rou‐
tine function-name (and its descendants) as -e,
below, and also exclude the time spent in function-
name (and its descendants) from the total and per‐
centage time computations. More than one -E option
may be given. For example:
-E mcount -E mcleanup
is the default.
-ffunction-name Print the graph profile entry only for routine func‐
tion-name and its descendants. More than one -f
option may be given. Only one function-name may be
given with each -f option.
-Ffunction-name Print the graph profile entry only for routine func‐
tion-name and its descendants (as -f, below) and
also use only the times of the printed routines in
total time and percentage computations. More than
one -F option may be given. Only one function-name
may be given with each -F option. The -F option
overrides the -E option.
-l Suppress the reporting of graph profile entries for
all local symbols. This option would be the equiva‐
lent of placing all of the local symbols for the
specified executable image on the -E exclusion list.
-n Limits the size of flat and graph profile listings
to the top n offending functions.
-s Produce a profile file gmon.sum which represents the
sum of the profile information in all of the speci‐
fied profile files. This summary profile file may
be given to subsequent executions of gprof (also
with -s) to accumulate profile data across several
runs of an a.out file. See also the -D option.
-z Display routines which have zero usage (as indicated
by call counts and accumulated time). This is useful
in conjunction with the -c option for discovering
which routines were never called. Note that this has
restricted use for dynamically linked executables,
since shared object text space will not be examined
by the -c option.
ENVIRONMENT VARIABLES
PROFDIR If this environment variable contains a value, place profil‐
ing output within that directory, in a file named pid.pro‐
gramname. pid is the process ID and programname is the name
of the program being profiled, as determined by removing any
path prefix from the argv[0] with which the program was
called. If the variable contains a null value, no profiling
output is produced. Otherwise, profiling output is placed
in the file gmon.out.
FILES
a.out executable file containing namelist
gmon.out dynamic call-graph and profile
gmon.sum summarized dynamic call-graph and profile
$PROFDIR/pid.programname
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │developer/object-file │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOcc(1), ld.so.1(1), prof(1), exit(2), pcsample(2), profil(2), mal‐
loc(3C), malloc(3MALLOC), monitor(3C), attributes(5), prof(5)
Graham, S.L., Kessler, P.B., McKusick, M.K., gprof: A Call Graph Execu‐
tion Profiler Proceedings of the SIGPLAN '82 Symposium on Compiler Con‐
struction, SIGPLAN Notices, Vol. 17, No. 6, pp. 120-126, June 1982.
Linker and Libraries Guide
NOTES
If the executable image has been stripped and does not have the .symtab
symbol table, gprof reads the global dynamic symbol tables .dynsym and
.SUNW_ldynsym, if present. The symbols in the dynamic symbol tables
are a subset of the symbols that are found in .symtab. The .dynsym sym‐
bol table contains the global symbols used by the runtime linker.
.SUNW_ldynsym augments the information in .dynsym with local function
symbols. In the case where .dynsym is found and .SUNW_ldynsym is not,
only the information for the global symbols is available. Without
local symbols, the behavior is as described for the -a option.
LD_LIBRARY_PATH must not contain /usr/lib as a component when compiling
a program for profiling. If LD_LIBRARY_PATH contains /usr/lib, the
program will not be linked correctly with the profiling versions of
the system libraries in /usr/lib/libp.
The times reported in successive identical runs may show variances
because of varying cache-hit ratios that result from sharing the cache
with other processes. Even if a program seems to be the only one using
the machine, hidden background or asynchronous processes may blur the
data. In rare cases, the clock ticks initiating recording of the pro‐
gram counter may beat with loops in a program, grossly distorting mea‐
surements. Call counts are always recorded precisely, however.
Only programs that call exit or return from main are guaranteed to pro‐
duce a profile file, unless a final call to monitor is explicitly
coded.
Functions such as mcount(), _mcount(), moncontrol(), _moncontrol(),
monitor(), and _monitor() may appear in the gprof report. These func‐
tions are part of the profiling implementation and thus account for
some amount of the runtime overhead. Since these functions are not
present in an unprofiled application, time accumulated and call counts
for these functions may be ignored when evaluating the performance of
an application.
64-bit profiling
64-bit profiling may be used freely with dynamically linked executa‐
bles, and profiling information is collected for the shared objects if
the objects are compiled for profiling. Care must be applied to inter‐
pret the profile output, since it is possible for symbols from differ‐
ent shared objects to have the same name. If name duplication occurs in
the profile output, the module id prefix before the symbol name in the
symbol index listing can be used to identify the appropriate module for
the symbol.
When using the -s or -Doption to sum multiple profile files, care must
be taken not to mix 32-bit profile files with 64-bit profile files.
32-bit profiling
32-bit profiling may be used with dynamically linked executables, but
care must be applied. In 32-bit profiling, shared objects cannot be
profiled with gprof. Thus, when a profiled, dynamically linked program
is executed, only the main portion of the image is sampled. This means
that all time spent outside of the main object, that is, time spent in
a shared object, will not be included in the profile summary; the total
time reported for the program may be less than the total time used by
the program.
Because the time spent in a shared object cannot be accounted for, the
use of shared objects should be minimized whenever a program is pro‐
filed with gprof. If desired, the program should be linked to the pro‐
filed version of a library (or to the standard archive version if no
profiling version is available), instead of the shared object to get
profile information on the functions of a library. Versions of profiled
libraries may be supplied with the system in the /usr/lib/libp direc‐
tory. Refer to compiler driver documentation on profiling.
Consider an extreme case. A profiled program dynamically linked with
the shared C library spends 100 units of time in some libc routine,
say, malloc(). Suppose malloc() is called only from routine B and B
consumes only 1 unit of time. Suppose further that routine A consumes
10 units of time, more than any other routine in the main (profiled)
portion of the image. In this case, gprof will conclude that most of
the time is being spent in A and almost no time is being spent in B.
From this it will be almost impossible to tell that the greatest
improvement can be made by looking at routine B and not routine A. The
value of the profiler in this case is severely degraded; the solution
is to use archives as much as possible for profiling.
BUGS
Parents which are not themselves profiled will have the time of their
profiled children propagated to them, but they will appear to be spon‐
taneously invoked in the call-graph listing, and will not have their
time propagated further. Similarly, signal catchers, even though pro‐
filed, will appear to be spontaneous (although for more obscure rea‐
sons). 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.
SunOS 5.11 8 Feb 2007 gprof(1)
