Linux gprof command
Updated: 11/06/2021 by Computer Hope
On Unix-like operating systems, the gprof command is a software developement tool that displays call graph profile data of a compiled binary.
This page covers the GNU/Linux version of gprof.
Description
gprof produces an execution profile of C, Pascal, or Fortran77 programs. The effect of called routines is incorporated in the profile of each caller. The profile data is taken from the call graph profile file (gmon.out, by default) which is created by programs that are compiled with the -pg option of cc, pc, and f77. The -pg option also links in versions of the library routines that are compiled for profiling. gprof reads the given object file (the default is a.out) and establishes the relation between its symbol table and the call graph profile from gmon.out. If more than one profile file is specified, the gprof output shows the sum of the profile information in the given profile files.
If you use gcc 2.95.x or 3.0 to compile your binaries, you may need to add the -fprofile-arcs to the compile command line for the call graphs to be properly stored in gmon.out.
gprof calculates the amount of time spent in each routine. Next, these times 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.
Several forms of output are available from the analysis:
- The flat profile shows how much time your program spent in each function, and how many times that function was called. To know which functions burn most of the cycles, it is stated concisely here.
- The call graph shows, for each function, which functions called it, which other functions it called, and how many times. There is also an estimate of how much time was spent in the subroutines of each function. This can suggest places where you might try to eliminate function calls that use a lot of time.
- The annotated source listing is a copy of the program's source code, labeled with the number of times each line of the program was executed.
Syntax
gprof [ -[abcDhilLrsTvwxyz] ] [ -[ACeEfFJnNOpPqQZ][name] ] [ -I dirs ]
[ -d[num] ] [ -k from/to ] [ -m min-count ] [ -R map_file ]
[ -t table-length ] [ --[no-]annotated-source[=name] ]
[ --[no-]exec-counts[=name] ] [ --[no-]flat-profile[=name] ]
[ --[no-]graph[=name] ] [ --[no-]time=name] [ --all-lines ] [ --brief ]
[ --debug[=level] ] [ --function-ordering ] [ --file-ordering map_file ]
[ --directory-path=dirs ] [ --display-unused-functions ]
[ --file-format=name ] [ --file-info ] [ --help ] [ --line ]
[ --min-count=n ] [ --no-static ] [ --print-path ] [ --separate-files ]
[ --static-call-graph ] [ --sum ] [ --table-length=len ]
[ --traditional ] [ --version ] [ --width=n ] [ --ignore-non-functions ]
[ --demangle[=STYLE] ] [ --no-demangle ] [--external-symbol-table=name]
[ image-file ] [ profile-file ... ]
Options
These options specify which of several output formats gprof should produce.
Many of these options take an optional symspec to specify functions to be included or excluded. These options can be specified multiple times, with different symspecs, to include or exclude sets of symbols.
Specifying any of these options overrides the default (-p -q), which prints a flat profile and call graph analysis for all functions.
| -A[symspec], --annotated-source[=symspec] |
The -A option causes gprof to print annotated source code. If symspec is specified, print output only for matching symbols. |
| -b, --brief | If the -b option is given, gprof doesn't print the verbose blurbs that try to explain the meaning of all of the fields in the tables. This is useful if you intend to print out the output, or are tired of seeing the blurbs. |
| -C[symspec], --exec-counts[=symspec] |
The -C option causes gprof to print a tally of functions and the number of times each was called. If symspec is specified, print tally only for matching symbols. If the profile data file contains basic-block count records, specifying the -l option, along with -C, causes basic-block execution counts to be tallied and displayed. |
| -i, --file-info | The -i option causes gprof to display summary information about the profile data file(s) and then exit. The number of histogram, call graph, and basic-block count records is displayed. |
| -I dirs, --directory-path=dirs |
The -I option specifies a list of search directories where to find source files. Environment variable GPROF_PATH can also be used to convey this information. Used mostly for annotated source output. |
| -J[symspec], --no-annotated-source[=symspec] |
The -J option causes gprof not to print annotated source code. If symspec is specified, gprof prints annotated source, but excludes matching symbols. |
| -L, --print-path | Normally, source filenames are printed with the path component suppressed. The -L option causes gprof to print the full pathname of source filenames, which is determined from symbolic debugging information in the image file and is relative to the directory where the compiler was invoked. |
| -p[symspec], --flat-profile[=symspec] |
The -p option causes gprof to print a flat profile. If symspec is specified, print flat profile only for matching symbols. |
| -P[symspec], --no-flat-profile[=symspec] |
The -P option causes gprof to suppress printing a flat profile. If symspec is specified, gprof prints a flat profile, but excludes matching symbols. |
| -q[symspec], --graph[=symspec] |
The -q option causes gprof to print the call graph analysis. If symspec is specified, print call graph only for matching symbols and their children. |
| -Q[symspec], --no-graph[=symspec] |
The -Q option causes gprof to suppress printing the call graph. If symspec is specified, gprof prints a call graph, but excludes matching symbols. |
| -t, --table-length=num | The -t option causes the num most active source lines in each source file to be listed when source annotation is enabled. The default is 10. |
| -y, --separate-files | This option affects annotated source output only. Normally, gprof prints annotated source files to standard output. If this option is specified, annotated source for a file named path/filename is generated in the file filename-ann. If the underlying file system would truncate filename-ann so that it overwrites the original filename, gprof generates annotated source in the file filename.ann instead (if the original file name has an extension, that extension is replaced with .ann). |
| -Z[symspec], --no-exec-counts[=symspec] |
The -Z option causes gprof not to print a tally of functions and the number of times each was called. If symspec is specified, print tally, but exclude matching symbols. |
| -r, --function-ordering | The --function-ordering option causes gprof to print a suggested function ordering for the program based on profiling data. This option suggests an ordering which may improve paging, tlb and cache behavior for the program on systems which support arbitrary ordering of functions in an executable. The exact details of how to force the linker to place functions in a particular order is system dependent and out of the scope of this manual. |
| -R map_file, --file-ordering map_file |
The --file-ordering option causes gprof to print a suggested .o link line ordering for the program based on profiling data. This option suggests an ordering which may improve paging, tlb and cache behavior for the program on systems which do not support arbitrary ordering of functions in an executable. Use of the -a argument is highly recommended with this option. The map_file argument is a pathname to a file which provides function name to object file mappings. The format of the file is similar to the output of the program nm. c-parse.o:00000000 T yyparsec-parse.o:00000004 C yyerrflagc-lang.o:00000000 T maybe_objc_method_namec-lang.o:00000000 T print_lang_statisticsc-lang.o:00000000 T recognize_objc_keywordc-decl.o:00000000 T print_lang_identifierc-decl.o:00000000 T print_lang_type...To create a map_file with GNU nm, type a command like "nm --extern-only --defined-only -v --print-file-name program-name". |
| -T, --traditional | The -T option causes gprof to print its output in "traditional" BSD style. |
| -w width, --width=width | Sets width of output lines to width. Currently only used when printing the function index at the bottom of the call graph. |
| -x, --all-lines | This option affects annotated source output only. By default, only the lines at the beginning of a basic-block are annotated. If this option is specified, every line in a basic-block is annotated by repeating the annotation for the first line. |
| --demangle[=style], --no-demangle |
These options control whether C++ symbol names should be demangled when printing output. The default is to demangle symbols. The --no-demangle option may be used to turn off demangling. Different compilers have different mangling styles. The optional demangling style argument can choose an appropriate demangling style for your compiler. |
Analysis options
| -a, --no-static | The -a option causes gprof to suppress the printing of statically declared (private) functions. (These are functions whose names are not listed as global, and that are not visible outside the file/function/block where they were defined.) Time spent in these functions, calls to/from them, etc., will all be attributed to the function that was loaded directly before it in the executable file. This option affects both the flat profile and the call graph. |
| -c, --static-call-graph |
The -c option causes the call graph of the program to be augmented by a heuristic which examines the text space of the object file and identifies function calls in the binary machine code. Since normal call graph records are only generated when functions are entered, this option identifies children that could be called, but never were. Calls to functions that were not compiled with profiling enabled are also identified, but only if symbol table entries are present for them. Calls to dynamic library routines are often not found by this option. Parents or children identified via this heuristic are indicated in the call graph with call counts of 0. |
| -D, --ignore-non-functions |
The -D option causes gprof to ignore symbols that are not known to be functions. This option gives more accurate profile data on systems where it is supported (Solaris and HPUX for example). |
| -k from/to | The -k option allows you to delete from the call graph any arcs from symbols matching symspec from to those matching symspec to. |
| -l --line | The -l option enables line-by-line profiling, which causes histogram hits to be charged to individual source code lines, instead of functions. This feature only works with programs compiled by older versions of the gcc compiler. Newer versions of gcc are designed to work with the gcov tool instead. If the program was compiled with basic-block counting enabled, this option also identifies how many times each line of code was executed. While line-by-line profiling help isolate where in a large function a program is spending its time, it also significantly increases the running time of gprof, and magnifies statistical inaccuracies. |
| -m num, --min-count=num |
This option affects execution count output only. Symbols that are executed less than num times are suppressed. |
| -nsymspec, --time=symspec |
The -n option causes gprof, in its call graph analysis, to only propagate times for symbols matching symspec. |
| -Nsymspec, --no-time=symspec |
The -n option causes gprof, in its call graph analysis, not to propagate times for symbols matching symspec. |
| -Sfilename, --external-symbol-table=filename |
The -S option causes gprof to read an external symbol table file, such as /proc/kallsyms, rather than read the symbol table from the given object file (the default is "a.out"). This is useful for profiling kernel modules. |
| -z, --display-unused-functions |
If you give the -z option, gprof will mention all functions in the flat profile, even those that were never called, and that had no time spent in them. This is useful in conjunction with the -c option for discovering which routines were never called. |
Miscellaneous Options
| -d[num], --debug[=num] |
The -d num option specifies debugging options. If num is not specified, enable all debugging. |
| -h, --help | The -h option prints command line usage. |
| -Oname, --file-format=name |
Selects the format of the profile data files. Recognized formats are auto (the default), bsd, 4.4bsd, magic, and prof (not yet supported). |
| -s, --sum | The -s option causes gprof to summarize the information in the profile data files it read in, and write out a profile data file called gmon.sum, which contains all the information from the profile data files that gprof read in. The file gmon.sum may be one of the specified input files; the effect of this is to merge the data in the other input files into gmon.sum. Eventually you can run gprof again without -s to analyze the cumulative data in the file gmon.sum. |
| -v, --version | The -v flag causes gprof to print the current version number, and then exit. |
Deprecated options
These options are replaced with newer versions that use symspecs.
| -e function_name | The -e function option tells gprof to not print information about the function function_name (and its children...) in the call graph. The function is listed as a child of any functions that call it, but its index number is shown as [not printed]. More than one -e option may be given; only one function_name may be indicated with each -e option. |
| -E function_name | The -E function option works like the -e option, but time spent in the function (and children who were not called from anywhere else), is not used to compute the percentages-of-time for the call graph. More than one -E option may be given; only one function_name may be indicated with each -E option. |
| -f function_name | The -f function option causes gprof to limit the call graph to the function function_name and its children (and their children...). More than one -f option may be given; only one function_name may be indicated with each -f option. |
| -F function_name | The -F function option works like the -f option, but only time spent in the function and its children (and their children...) will be used to determine total-time and percentages-of-time for the call graph. More than one -F option may be given; only one function_name may be indicated with each -F option. The -F option overrides the -E option. |
Files
| a.out | the namelist and text space. |
| gmon.out | dynamic call graph and profile. |
| gmon.sum | summarized dynamic call graph and profile. |
Related commands
cc — Compiler of the C programming language.