gprof.info revision 1.1
1This is gprof.info, produced by makeinfo version 4.8 from gprof.texi. 2 3INFO-DIR-SECTION Software development 4START-INFO-DIR-ENTRY 5* gprof: (gprof). Profiling your program's execution 6END-INFO-DIR-ENTRY 7 8 This file documents the gprof profiler of the GNU system. 9 10 Copyright (C) 1988, 1992, 1997, 1998, 1999, 2000, 2001, 2003, 2007, 112008, 2009 Free Software Foundation, Inc. 12 13 Permission is granted to copy, distribute and/or modify this document 14under the terms of the GNU Free Documentation License, Version 1.3 or 15any later version published by the Free Software Foundation; with no 16Invariant Sections, with no Front-Cover Texts, and with no Back-Cover 17Texts. A copy of the license is included in the section entitled "GNU 18Free Documentation License". 19 20 21File: gprof.info, Node: Top, Next: Introduction, Up: (dir) 22 23Profiling a Program: Where Does It Spend Its Time? 24************************************************** 25 26This manual describes the GNU profiler, `gprof', and how you can use it 27to determine which parts of a program are taking most of the execution 28time. We assume that you know how to write, compile, and execute 29programs. GNU `gprof' was written by Jay Fenlason. 30 31 This manual is for `gprof' (GNU Binutils) version 2.23.1. 32 33 This document is distributed under the terms of the GNU Free 34Documentation License version 1.3. A copy of the license is included 35in the section entitled "GNU Free Documentation License". 36 37* Menu: 38 39* Introduction:: What profiling means, and why it is useful. 40 41* Compiling:: How to compile your program for profiling. 42* Executing:: Executing your program to generate profile data 43* Invoking:: How to run `gprof', and its options 44 45* Output:: Interpreting `gprof''s output 46 47* Inaccuracy:: Potential problems you should be aware of 48* How do I?:: Answers to common questions 49* Incompatibilities:: (between GNU `gprof' and Unix `gprof'.) 50* Details:: Details of how profiling is done 51* GNU Free Documentation License:: GNU Free Documentation License 52 53 54File: gprof.info, Node: Introduction, Next: Compiling, Prev: Top, Up: Top 55 561 Introduction to Profiling 57*************************** 58 59Profiling allows you to learn where your program spent its time and 60which functions called which other functions while it was executing. 61This information can show you which pieces of your program are slower 62than you expected, and might be candidates for rewriting to make your 63program execute faster. It can also tell you which functions are being 64called more or less often than you expected. This may help you spot 65bugs that had otherwise been unnoticed. 66 67 Since the profiler uses information collected during the actual 68execution of your program, it can be used on programs that are too 69large or too complex to analyze by reading the source. However, how 70your program is run will affect the information that shows up in the 71profile data. If you don't use some feature of your program while it 72is being profiled, no profile information will be generated for that 73feature. 74 75 Profiling has several steps: 76 77 * You must compile and link your program with profiling enabled. 78 *Note Compiling a Program for Profiling: Compiling. 79 80 * You must execute your program to generate a profile data file. 81 *Note Executing the Program: Executing. 82 83 * You must run `gprof' to analyze the profile data. *Note `gprof' 84 Command Summary: Invoking. 85 86 The next three chapters explain these steps in greater detail. 87 88 Several forms of output are available from the analysis. 89 90 The "flat profile" shows how much time your program spent in each 91function, and how many times that function was called. If you simply 92want to know which functions burn most of the cycles, it is stated 93concisely here. *Note The Flat Profile: Flat Profile. 94 95 The "call graph" shows, for each function, which functions called 96it, which other functions it called, and how many times. There is also 97an estimate of how much time was spent in the subroutines of each 98function. This can suggest places where you might try to eliminate 99function calls that use a lot of time. *Note The Call Graph: Call 100Graph. 101 102 The "annotated source" listing is a copy of the program's source 103code, labeled with the number of times each line of the program was 104executed. *Note The Annotated Source Listing: Annotated Source. 105 106 To better understand how profiling works, you may wish to read a 107description of its implementation. *Note Implementation of Profiling: 108Implementation. 109 110 111File: gprof.info, Node: Compiling, Next: Executing, Prev: Introduction, Up: Top 112 1132 Compiling a Program for Profiling 114*********************************** 115 116The first step in generating profile information for your program is to 117compile and link it with profiling enabled. 118 119 To compile a source file for profiling, specify the `-pg' option when 120you run the compiler. (This is in addition to the options you normally 121use.) 122 123 To link the program for profiling, if you use a compiler such as `cc' 124to do the linking, simply specify `-pg' in addition to your usual 125options. The same option, `-pg', alters either compilation or linking 126to do what is necessary for profiling. Here are examples: 127 128 cc -g -c myprog.c utils.c -pg 129 cc -o myprog myprog.o utils.o -pg 130 131 The `-pg' option also works with a command that both compiles and 132links: 133 134 cc -o myprog myprog.c utils.c -g -pg 135 136 Note: The `-pg' option must be part of your compilation options as 137well as your link options. If it is not then no call-graph data will 138be gathered and when you run `gprof' you will get an error message like 139this: 140 141 gprof: gmon.out file is missing call-graph data 142 143 If you add the `-Q' switch to suppress the printing of the call 144graph data you will still be able to see the time samples: 145 146 Flat profile: 147 148 Each sample counts as 0.01 seconds. 149 % cumulative self self total 150 time seconds seconds calls Ts/call Ts/call name 151 44.12 0.07 0.07 zazLoop 152 35.29 0.14 0.06 main 153 20.59 0.17 0.04 bazMillion 154 155 If you run the linker `ld' directly instead of through a compiler 156such as `cc', you may have to specify a profiling startup file 157`gcrt0.o' as the first input file instead of the usual startup file 158`crt0.o'. In addition, you would probably want to specify the 159profiling C library, `libc_p.a', by writing `-lc_p' instead of the 160usual `-lc'. This is not absolutely necessary, but doing this gives 161you number-of-calls information for standard library functions such as 162`read' and `open'. For example: 163 164 ld -o myprog /lib/gcrt0.o myprog.o utils.o -lc_p 165 166 If you are running the program on a system which supports shared 167libraries you may run into problems with the profiling support code in 168a shared library being called before that library has been fully 169initialised. This is usually detected by the program encountering a 170segmentation fault as soon as it is run. The solution is to link 171against a static version of the library containing the profiling 172support code, which for `gcc' users can be done via the `-static' or 173`-static-libgcc' command line option. For example: 174 175 gcc -g -pg -static-libgcc myprog.c utils.c -o myprog 176 177 If you compile only some of the modules of the program with `-pg', 178you can still profile the program, but you won't get complete 179information about the modules that were compiled without `-pg'. The 180only information you get for the functions in those modules is the 181total time spent in them; there is no record of how many times they 182were called, or from where. This will not affect the flat profile 183(except that the `calls' field for the functions will be blank), but 184will greatly reduce the usefulness of the call graph. 185 186 If you wish to perform line-by-line profiling you should use the 187`gcov' tool instead of `gprof'. See that tool's manual or info pages 188for more details of how to do this. 189 190 Note, older versions of `gcc' produce line-by-line profiling 191information that works with `gprof' rather than `gcov' so there is 192still support for displaying this kind of information in `gprof'. *Note 193Line-by-line Profiling: Line-by-line. 194 195 It also worth noting that `gcc' implements a 196`-finstrument-functions' command line option which will insert calls to 197special user supplied instrumentation routines at the entry and exit of 198every function in their program. This can be used to implement an 199alternative profiling scheme. 200 201 202File: gprof.info, Node: Executing, Next: Invoking, Prev: Compiling, Up: Top 203 2043 Executing the Program 205*********************** 206 207Once the program is compiled for profiling, you must run it in order to 208generate the information that `gprof' needs. Simply run the program as 209usual, using the normal arguments, file names, etc. The program should 210run normally, producing the same output as usual. It will, however, run 211somewhat slower than normal because of the time spent collecting and 212writing the profile data. 213 214 The way you run the program--the arguments and input that you give 215it--may have a dramatic effect on what the profile information shows. 216The profile data will describe the parts of the program that were 217activated for the particular input you use. For example, if the first 218command you give to your program is to quit, the profile data will show 219the time used in initialization and in cleanup, but not much else. 220 221 Your program will write the profile data into a file called 222`gmon.out' just before exiting. If there is already a file called 223`gmon.out', its contents are overwritten. There is currently no way to 224tell the program to write the profile data under a different name, but 225you can rename the file afterwards if you are concerned that it may be 226overwritten. 227 228 In order to write the `gmon.out' file properly, your program must 229exit normally: by returning from `main' or by calling `exit'. Calling 230the low-level function `_exit' does not write the profile data, and 231neither does abnormal termination due to an unhandled signal. 232 233 The `gmon.out' file is written in the program's _current working 234directory_ at the time it exits. This means that if your program calls 235`chdir', the `gmon.out' file will be left in the last directory your 236program `chdir''d to. If you don't have permission to write in this 237directory, the file is not written, and you will get an error message. 238 239 Older versions of the GNU profiling library may also write a file 240called `bb.out'. This file, if present, contains an human-readable 241listing of the basic-block execution counts. Unfortunately, the 242appearance of a human-readable `bb.out' means the basic-block counts 243didn't get written into `gmon.out'. The Perl script `bbconv.pl', 244included with the `gprof' source distribution, will convert a `bb.out' 245file into a format readable by `gprof'. Invoke it like this: 246 247 bbconv.pl < bb.out > BH-DATA 248 249 This translates the information in `bb.out' into a form that `gprof' 250can understand. But you still need to tell `gprof' about the existence 251of this translated information. To do that, include BB-DATA on the 252`gprof' command line, _along with `gmon.out'_, like this: 253 254 gprof OPTIONS EXECUTABLE-FILE gmon.out BB-DATA [YET-MORE-PROFILE-DATA-FILES...] [> OUTFILE] 255 256 257File: gprof.info, Node: Invoking, Next: Output, Prev: Executing, Up: Top 258 2594 `gprof' Command Summary 260************************* 261 262After you have a profile data file `gmon.out', you can run `gprof' to 263interpret the information in it. The `gprof' program prints a flat 264profile and a call graph on standard output. Typically you would 265redirect the output of `gprof' into a file with `>'. 266 267 You run `gprof' like this: 268 269 gprof OPTIONS [EXECUTABLE-FILE [PROFILE-DATA-FILES...]] [> OUTFILE] 270 271Here square-brackets indicate optional arguments. 272 273 If you omit the executable file name, the file `a.out' is used. If 274you give no profile data file name, the file `gmon.out' is used. If 275any file is not in the proper format, or if the profile data file does 276not appear to belong to the executable file, an error message is 277printed. 278 279 You can give more than one profile data file by entering all their 280names after the executable file name; then the statistics in all the 281data files are summed together. 282 283 The order of these options does not matter. 284 285* Menu: 286 287* Output Options:: Controlling `gprof''s output style 288* Analysis Options:: Controlling how `gprof' analyzes its data 289* Miscellaneous Options:: 290* Deprecated Options:: Options you no longer need to use, but which 291 have been retained for compatibility 292* Symspecs:: Specifying functions to include or exclude 293 294 295File: gprof.info, Node: Output Options, Next: Analysis Options, Up: Invoking 296 2974.1 Output Options 298================== 299 300These options specify which of several output formats `gprof' should 301produce. 302 303 Many of these options take an optional "symspec" to specify 304functions to be included or excluded. These options can be specified 305multiple times, with different symspecs, to include or exclude sets of 306symbols. *Note Symspecs: Symspecs. 307 308 Specifying any of these options overrides the default (`-p -q'), 309which prints a flat profile and call graph analysis for all functions. 310 311`-A[SYMSPEC]' 312`--annotated-source[=SYMSPEC]' 313 The `-A' option causes `gprof' to print annotated source code. If 314 SYMSPEC is specified, print output only for matching symbols. 315 *Note The Annotated Source Listing: Annotated Source. 316 317`-b' 318`--brief' 319 If the `-b' option is given, `gprof' doesn't print the verbose 320 blurbs that try to explain the meaning of all of the fields in the 321 tables. This is useful if you intend to print out the output, or 322 are tired of seeing the blurbs. 323 324`-C[SYMSPEC]' 325`--exec-counts[=SYMSPEC]' 326 The `-C' option causes `gprof' to print a tally of functions and 327 the number of times each was called. If SYMSPEC is specified, 328 print tally only for matching symbols. 329 330 If the profile data file contains basic-block count records, 331 specifying the `-l' option, along with `-C', will cause basic-block 332 execution counts to be tallied and displayed. 333 334`-i' 335`--file-info' 336 The `-i' option causes `gprof' to display summary information 337 about the profile data file(s) and then exit. The number of 338 histogram, call graph, and basic-block count records is displayed. 339 340`-I DIRS' 341`--directory-path=DIRS' 342 The `-I' option specifies a list of search directories in which to 343 find source files. Environment variable GPROF_PATH can also be 344 used to convey this information. Used mostly for annotated source 345 output. 346 347`-J[SYMSPEC]' 348`--no-annotated-source[=SYMSPEC]' 349 The `-J' option causes `gprof' not to print annotated source code. 350 If SYMSPEC is specified, `gprof' prints annotated source, but 351 excludes matching symbols. 352 353`-L' 354`--print-path' 355 Normally, source filenames are printed with the path component 356 suppressed. The `-L' option causes `gprof' to print the full 357 pathname of source filenames, which is determined from symbolic 358 debugging information in the image file and is relative to the 359 directory in which the compiler was invoked. 360 361`-p[SYMSPEC]' 362`--flat-profile[=SYMSPEC]' 363 The `-p' option causes `gprof' to print a flat profile. If 364 SYMSPEC is specified, print flat profile only for matching symbols. 365 *Note The Flat Profile: Flat Profile. 366 367`-P[SYMSPEC]' 368`--no-flat-profile[=SYMSPEC]' 369 The `-P' option causes `gprof' to suppress printing a flat profile. 370 If SYMSPEC is specified, `gprof' prints a flat profile, but 371 excludes matching symbols. 372 373`-q[SYMSPEC]' 374`--graph[=SYMSPEC]' 375 The `-q' option causes `gprof' to print the call graph analysis. 376 If SYMSPEC is specified, print call graph only for matching symbols 377 and their children. *Note The Call Graph: Call Graph. 378 379`-Q[SYMSPEC]' 380`--no-graph[=SYMSPEC]' 381 The `-Q' option causes `gprof' to suppress printing the call graph. 382 If SYMSPEC is specified, `gprof' prints a call graph, but excludes 383 matching symbols. 384 385`-t' 386`--table-length=NUM' 387 The `-t' option causes the NUM most active source lines in each 388 source file to be listed when source annotation is enabled. The 389 default is 10. 390 391`-y' 392`--separate-files' 393 This option affects annotated source output only. Normally, 394 `gprof' prints annotated source files to standard-output. If this 395 option is specified, annotated source for a file named 396 `path/FILENAME' is generated in the file `FILENAME-ann'. If the 397 underlying file system would truncate `FILENAME-ann' so that it 398 overwrites the original `FILENAME', `gprof' generates annotated 399 source in the file `FILENAME.ann' instead (if the original file 400 name has an extension, that extension is _replaced_ with `.ann'). 401 402`-Z[SYMSPEC]' 403`--no-exec-counts[=SYMSPEC]' 404 The `-Z' option causes `gprof' not to print a tally of functions 405 and the number of times each was called. If SYMSPEC is specified, 406 print tally, but exclude matching symbols. 407 408`-r' 409`--function-ordering' 410 The `--function-ordering' option causes `gprof' to print a 411 suggested function ordering for the program based on profiling 412 data. This option suggests an ordering which may improve paging, 413 tlb and cache behavior for the program on systems which support 414 arbitrary ordering of functions in an executable. 415 416 The exact details of how to force the linker to place functions in 417 a particular order is system dependent and out of the scope of this 418 manual. 419 420`-R MAP_FILE' 421`--file-ordering MAP_FILE' 422 The `--file-ordering' option causes `gprof' to print a suggested 423 .o link line ordering for the program based on profiling data. 424 This option suggests an ordering which may improve paging, tlb and 425 cache behavior for the program on systems which do not support 426 arbitrary ordering of functions in an executable. 427 428 Use of the `-a' argument is highly recommended with this option. 429 430 The MAP_FILE argument is a pathname to a file which provides 431 function name to object file mappings. The format of the file is 432 similar to the output of the program `nm'. 433 434 c-parse.o:00000000 T yyparse 435 c-parse.o:00000004 C yyerrflag 436 c-lang.o:00000000 T maybe_objc_method_name 437 c-lang.o:00000000 T print_lang_statistics 438 c-lang.o:00000000 T recognize_objc_keyword 439 c-decl.o:00000000 T print_lang_identifier 440 c-decl.o:00000000 T print_lang_type 441 ... 442 443 To create a MAP_FILE with GNU `nm', type a command like `nm 444 --extern-only --defined-only -v --print-file-name program-name'. 445 446`-T' 447`--traditional' 448 The `-T' option causes `gprof' to print its output in 449 "traditional" BSD style. 450 451`-w WIDTH' 452`--width=WIDTH' 453 Sets width of output lines to WIDTH. Currently only used when 454 printing the function index at the bottom of the call graph. 455 456`-x' 457`--all-lines' 458 This option affects annotated source output only. By default, 459 only the lines at the beginning of a basic-block are annotated. 460 If this option is specified, every line in a basic-block is 461 annotated by repeating the annotation for the first line. This 462 behavior is similar to `tcov''s `-a'. 463 464`--demangle[=STYLE]' 465`--no-demangle' 466 These options control whether C++ symbol names should be demangled 467 when printing output. The default is to demangle symbols. The 468 `--no-demangle' option may be used to turn off demangling. 469 Different compilers have different mangling styles. The optional 470 demangling style argument can be used to choose an appropriate 471 demangling style for your compiler. 472 473 474File: gprof.info, Node: Analysis Options, Next: Miscellaneous Options, Prev: Output Options, Up: Invoking 475 4764.2 Analysis Options 477==================== 478 479`-a' 480`--no-static' 481 The `-a' option causes `gprof' to suppress the printing of 482 statically declared (private) functions. (These are functions 483 whose names are not listed as global, and which are not visible 484 outside the file/function/block where they were defined.) Time 485 spent in these functions, calls to/from them, etc., will all be 486 attributed to the function that was loaded directly before it in 487 the executable file. This option affects both the flat profile 488 and the call graph. 489 490`-c' 491`--static-call-graph' 492 The `-c' option causes the call graph of the program to be 493 augmented by a heuristic which examines the text space of the 494 object file and identifies function calls in the binary machine 495 code. Since normal call graph records are only generated when 496 functions are entered, this option identifies children that could 497 have been called, but never were. Calls to functions that were 498 not compiled with profiling enabled are also identified, but only 499 if symbol table entries are present for them. Calls to dynamic 500 library routines are typically _not_ found by this option. 501 Parents or children identified via this heuristic are indicated in 502 the call graph with call counts of `0'. 503 504`-D' 505`--ignore-non-functions' 506 The `-D' option causes `gprof' to ignore symbols which are not 507 known to be functions. This option will give more accurate 508 profile data on systems where it is supported (Solaris and HPUX for 509 example). 510 511`-k FROM/TO' 512 The `-k' option allows you to delete from the call graph any arcs 513 from symbols matching symspec FROM to those matching symspec TO. 514 515`-l' 516`--line' 517 The `-l' option enables line-by-line profiling, which causes 518 histogram hits to be charged to individual source code lines, 519 instead of functions. This feature only works with programs 520 compiled by older versions of the `gcc' compiler. Newer versions 521 of `gcc' are designed to work with the `gcov' tool instead. 522 523 If the program was compiled with basic-block counting enabled, 524 this option will also identify how many times each line of code 525 was executed. While line-by-line profiling can help isolate where 526 in a large function a program is spending its time, it also 527 significantly increases the running time of `gprof', and magnifies 528 statistical inaccuracies. *Note Statistical Sampling Error: 529 Sampling Error. 530 531`-m NUM' 532`--min-count=NUM' 533 This option affects execution count output only. Symbols that are 534 executed less than NUM times are suppressed. 535 536`-nSYMSPEC' 537`--time=SYMSPEC' 538 The `-n' option causes `gprof', in its call graph analysis, to 539 only propagate times for symbols matching SYMSPEC. 540 541`-NSYMSPEC' 542`--no-time=SYMSPEC' 543 The `-n' option causes `gprof', in its call graph analysis, not to 544 propagate times for symbols matching SYMSPEC. 545 546`-SFILENAME' 547`--external-symbol-table=FILENAME' 548 The `-S' option causes `gprof' to read an external symbol table 549 file, such as `/proc/kallsyms', rather than read the symbol table 550 from the given object file (the default is `a.out'). This is useful 551 for profiling kernel modules. 552 553`-z' 554`--display-unused-functions' 555 If you give the `-z' option, `gprof' will mention all functions in 556 the flat profile, even those that were never called, and that had 557 no time spent in them. This is useful in conjunction with the 558 `-c' option for discovering which routines were never called. 559 560 561 562File: gprof.info, Node: Miscellaneous Options, Next: Deprecated Options, Prev: Analysis Options, Up: Invoking 563 5644.3 Miscellaneous Options 565========================= 566 567`-d[NUM]' 568`--debug[=NUM]' 569 The `-d NUM' option specifies debugging options. If NUM is not 570 specified, enable all debugging. *Note Debugging `gprof': 571 Debugging. 572 573`-h' 574`--help' 575 The `-h' option prints command line usage. 576 577`-ONAME' 578`--file-format=NAME' 579 Selects the format of the profile data files. Recognized formats 580 are `auto' (the default), `bsd', `4.4bsd', `magic', and `prof' 581 (not yet supported). 582 583`-s' 584`--sum' 585 The `-s' option causes `gprof' to summarize the information in the 586 profile data files it read in, and write out a profile data file 587 called `gmon.sum', which contains all the information from the 588 profile data files that `gprof' read in. The file `gmon.sum' may 589 be one of the specified input files; the effect of this is to 590 merge the data in the other input files into `gmon.sum'. 591 592 Eventually you can run `gprof' again without `-s' to analyze the 593 cumulative data in the file `gmon.sum'. 594 595`-v' 596`--version' 597 The `-v' flag causes `gprof' to print the current version number, 598 and then exit. 599 600 601 602File: gprof.info, Node: Deprecated Options, Next: Symspecs, Prev: Miscellaneous Options, Up: Invoking 603 6044.4 Deprecated Options 605====================== 606 607These options have been replaced with newer versions that use symspecs. 608 609`-e FUNCTION_NAME' 610 The `-e FUNCTION' option tells `gprof' to not print information 611 about the function FUNCTION_NAME (and its children...) in the call 612 graph. The function will still be listed as a child of any 613 functions that call it, but its index number will be shown as 614 `[not printed]'. More than one `-e' option may be given; only one 615 FUNCTION_NAME may be indicated with each `-e' option. 616 617`-E FUNCTION_NAME' 618 The `-E FUNCTION' option works like the `-e' option, but time 619 spent in the function (and children who were not called from 620 anywhere else), will not be used to compute the 621 percentages-of-time for the call graph. More than one `-E' option 622 may be given; only one FUNCTION_NAME may be indicated with each 623 `-E' option. 624 625`-f FUNCTION_NAME' 626 The `-f FUNCTION' option causes `gprof' to limit the call graph to 627 the function FUNCTION_NAME and its children (and their 628 children...). More than one `-f' option may be given; only one 629 FUNCTION_NAME may be indicated with each `-f' option. 630 631`-F FUNCTION_NAME' 632 The `-F FUNCTION' option works like the `-f' option, but only time 633 spent in the function and its children (and their children...) 634 will be used to determine total-time and percentages-of-time for 635 the call graph. More than one `-F' option may be given; only one 636 FUNCTION_NAME may be indicated with each `-F' option. The `-F' 637 option overrides the `-E' option. 638 639 640 Note that only one function can be specified with each `-e', `-E', 641`-f' or `-F' option. To specify more than one function, use multiple 642options. For example, this command: 643 644 gprof -e boring -f foo -f bar myprogram > gprof.output 645 646lists in the call graph all functions that were reached from either 647`foo' or `bar' and were not reachable from `boring'. 648 649 650File: gprof.info, Node: Symspecs, Prev: Deprecated Options, Up: Invoking 651 6524.5 Symspecs 653============ 654 655Many of the output options allow functions to be included or excluded 656using "symspecs" (symbol specifications), which observe the following 657syntax: 658 659 filename_containing_a_dot 660 | funcname_not_containing_a_dot 661 | linenumber 662 | ( [ any_filename ] `:' ( any_funcname | linenumber ) ) 663 664 Here are some sample symspecs: 665 666`main.c' 667 Selects everything in file `main.c'--the dot in the string tells 668 `gprof' to interpret the string as a filename, rather than as a 669 function name. To select a file whose name does not contain a 670 dot, a trailing colon should be specified. For example, `odd:' is 671 interpreted as the file named `odd'. 672 673`main' 674 Selects all functions named `main'. 675 676 Note that there may be multiple instances of the same function name 677 because some of the definitions may be local (i.e., static). 678 Unless a function name is unique in a program, you must use the 679 colon notation explained below to specify a function from a 680 specific source file. 681 682 Sometimes, function names contain dots. In such cases, it is 683 necessary to add a leading colon to the name. For example, 684 `:.mul' selects function `.mul'. 685 686 In some object file formats, symbols have a leading underscore. 687 `gprof' will normally not print these underscores. When you name a 688 symbol in a symspec, you should type it exactly as `gprof' prints 689 it in its output. For example, if the compiler produces a symbol 690 `_main' from your `main' function, `gprof' still prints it as 691 `main' in its output, so you should use `main' in symspecs. 692 693`main.c:main' 694 Selects function `main' in file `main.c'. 695 696`main.c:134' 697 Selects line 134 in file `main.c'. 698 699 700File: gprof.info, Node: Output, Next: Inaccuracy, Prev: Invoking, Up: Top 701 7025 Interpreting `gprof''s Output 703******************************* 704 705`gprof' can produce several different output styles, the most important 706of which are described below. The simplest output styles (file 707information, execution count, and function and file ordering) are not 708described here, but are documented with the respective options that 709trigger them. *Note Output Options: Output Options. 710 711* Menu: 712 713* Flat Profile:: The flat profile shows how much time was spent 714 executing directly in each function. 715* Call Graph:: The call graph shows which functions called which 716 others, and how much time each function used 717 when its subroutine calls are included. 718* Line-by-line:: `gprof' can analyze individual source code lines 719* Annotated Source:: The annotated source listing displays source code 720 labeled with execution counts 721 722 723File: gprof.info, Node: Flat Profile, Next: Call Graph, Up: Output 724 7255.1 The Flat Profile 726==================== 727 728The "flat profile" shows the total amount of time your program spent 729executing each function. Unless the `-z' option is given, functions 730with no apparent time spent in them, and no apparent calls to them, are 731not mentioned. Note that if a function was not compiled for profiling, 732and didn't run long enough to show up on the program counter histogram, 733it will be indistinguishable from a function that was never called. 734 735 This is part of a flat profile for a small program: 736 737 Flat profile: 738 739 Each sample counts as 0.01 seconds. 740 % cumulative self self total 741 time seconds seconds calls ms/call ms/call name 742 33.34 0.02 0.02 7208 0.00 0.00 open 743 16.67 0.03 0.01 244 0.04 0.12 offtime 744 16.67 0.04 0.01 8 1.25 1.25 memccpy 745 16.67 0.05 0.01 7 1.43 1.43 write 746 16.67 0.06 0.01 mcount 747 0.00 0.06 0.00 236 0.00 0.00 tzset 748 0.00 0.06 0.00 192 0.00 0.00 tolower 749 0.00 0.06 0.00 47 0.00 0.00 strlen 750 0.00 0.06 0.00 45 0.00 0.00 strchr 751 0.00 0.06 0.00 1 0.00 50.00 main 752 0.00 0.06 0.00 1 0.00 0.00 memcpy 753 0.00 0.06 0.00 1 0.00 10.11 print 754 0.00 0.06 0.00 1 0.00 0.00 profil 755 0.00 0.06 0.00 1 0.00 50.00 report 756 ... 757 758The functions are sorted first by decreasing run-time spent in them, 759then by decreasing number of calls, then alphabetically by name. The 760functions `mcount' and `profil' are part of the profiling apparatus and 761appear in every flat profile; their time gives a measure of the amount 762of overhead due to profiling. 763 764 Just before the column headers, a statement appears indicating how 765much time each sample counted as. This "sampling period" estimates the 766margin of error in each of the time figures. A time figure that is not 767much larger than this is not reliable. In this example, each sample 768counted as 0.01 seconds, suggesting a 100 Hz sampling rate. The 769program's total execution time was 0.06 seconds, as indicated by the 770`cumulative seconds' field. Since each sample counted for 0.01 771seconds, this means only six samples were taken during the run. Two of 772the samples occurred while the program was in the `open' function, as 773indicated by the `self seconds' field. Each of the other four samples 774occurred one each in `offtime', `memccpy', `write', and `mcount'. 775Since only six samples were taken, none of these values can be regarded 776as particularly reliable. In another run, the `self seconds' field for 777`mcount' might well be `0.00' or `0.02'. *Note Statistical Sampling 778Error: Sampling Error, for a complete discussion. 779 780 The remaining functions in the listing (those whose `self seconds' 781field is `0.00') didn't appear in the histogram samples at all. 782However, the call graph indicated that they were called, so therefore 783they are listed, sorted in decreasing order by the `calls' field. 784Clearly some time was spent executing these functions, but the paucity 785of histogram samples prevents any determination of how much time each 786took. 787 788 Here is what the fields in each line mean: 789 790`% time' 791 This is the percentage of the total execution time your program 792 spent in this function. These should all add up to 100%. 793 794`cumulative seconds' 795 This is the cumulative total number of seconds the computer spent 796 executing this functions, plus the time spent in all the functions 797 above this one in this table. 798 799`self seconds' 800 This is the number of seconds accounted for by this function alone. 801 The flat profile listing is sorted first by this number. 802 803`calls' 804 This is the total number of times the function was called. If the 805 function was never called, or the number of times it was called 806 cannot be determined (probably because the function was not 807 compiled with profiling enabled), the "calls" field is blank. 808 809`self ms/call' 810 This represents the average number of milliseconds spent in this 811 function per call, if this function is profiled. Otherwise, this 812 field is blank for this function. 813 814`total ms/call' 815 This represents the average number of milliseconds spent in this 816 function and its descendants per call, if this function is 817 profiled. Otherwise, this field is blank for this function. This 818 is the only field in the flat profile that uses call graph 819 analysis. 820 821`name' 822 This is the name of the function. The flat profile is sorted by 823 this field alphabetically after the "self seconds" and "calls" 824 fields are sorted. 825 826 827File: gprof.info, Node: Call Graph, Next: Line-by-line, Prev: Flat Profile, Up: Output 828 8295.2 The Call Graph 830================== 831 832The "call graph" shows how much time was spent in each function and its 833children. From this information, you can find functions that, while 834they themselves may not have used much time, called other functions 835that did use unusual amounts of time. 836 837 Here is a sample call from a small program. This call came from the 838same `gprof' run as the flat profile example in the previous section. 839 840 granularity: each sample hit covers 2 byte(s) for 20.00% of 0.05 seconds 841 842 index % time self children called name 843 <spontaneous> 844 [1] 100.0 0.00 0.05 start [1] 845 0.00 0.05 1/1 main [2] 846 0.00 0.00 1/2 on_exit [28] 847 0.00 0.00 1/1 exit [59] 848 ----------------------------------------------- 849 0.00 0.05 1/1 start [1] 850 [2] 100.0 0.00 0.05 1 main [2] 851 0.00 0.05 1/1 report [3] 852 ----------------------------------------------- 853 0.00 0.05 1/1 main [2] 854 [3] 100.0 0.00 0.05 1 report [3] 855 0.00 0.03 8/8 timelocal [6] 856 0.00 0.01 1/1 print [9] 857 0.00 0.01 9/9 fgets [12] 858 0.00 0.00 12/34 strncmp <cycle 1> [40] 859 0.00 0.00 8/8 lookup [20] 860 0.00 0.00 1/1 fopen [21] 861 0.00 0.00 8/8 chewtime [24] 862 0.00 0.00 8/16 skipspace [44] 863 ----------------------------------------------- 864 [4] 59.8 0.01 0.02 8+472 <cycle 2 as a whole> [4] 865 0.01 0.02 244+260 offtime <cycle 2> [7] 866 0.00 0.00 236+1 tzset <cycle 2> [26] 867 ----------------------------------------------- 868 869 The lines full of dashes divide this table into "entries", one for 870each function. Each entry has one or more lines. 871 872 In each entry, the primary line is the one that starts with an index 873number in square brackets. The end of this line says which function 874the entry is for. The preceding lines in the entry describe the 875callers of this function and the following lines describe its 876subroutines (also called "children" when we speak of the call graph). 877 878 The entries are sorted by time spent in the function and its 879subroutines. 880 881 The internal profiling function `mcount' (*note The Flat Profile: 882Flat Profile.) is never mentioned in the call graph. 883 884* Menu: 885 886* Primary:: Details of the primary line's contents. 887* Callers:: Details of caller-lines' contents. 888* Subroutines:: Details of subroutine-lines' contents. 889* Cycles:: When there are cycles of recursion, 890 such as `a' calls `b' calls `a'... 891 892 893File: gprof.info, Node: Primary, Next: Callers, Up: Call Graph 894 8955.2.1 The Primary Line 896---------------------- 897 898The "primary line" in a call graph entry is the line that describes the 899function which the entry is about and gives the overall statistics for 900this function. 901 902 For reference, we repeat the primary line from the entry for function 903`report' in our main example, together with the heading line that shows 904the names of the fields: 905 906 index % time self children called name 907 ... 908 [3] 100.0 0.00 0.05 1 report [3] 909 910 Here is what the fields in the primary line mean: 911 912`index' 913 Entries are numbered with consecutive integers. Each function 914 therefore has an index number, which appears at the beginning of 915 its primary line. 916 917 Each cross-reference to a function, as a caller or subroutine of 918 another, gives its index number as well as its name. The index 919 number guides you if you wish to look for the entry for that 920 function. 921 922`% time' 923 This is the percentage of the total time that was spent in this 924 function, including time spent in subroutines called from this 925 function. 926 927 The time spent in this function is counted again for the callers of 928 this function. Therefore, adding up these percentages is 929 meaningless. 930 931`self' 932 This is the total amount of time spent in this function. This 933 should be identical to the number printed in the `seconds' field 934 for this function in the flat profile. 935 936`children' 937 This is the total amount of time spent in the subroutine calls 938 made by this function. This should be equal to the sum of all the 939 `self' and `children' entries of the children listed directly 940 below this function. 941 942`called' 943 This is the number of times the function was called. 944 945 If the function called itself recursively, there are two numbers, 946 separated by a `+'. The first number counts non-recursive calls, 947 and the second counts recursive calls. 948 949 In the example above, the function `report' was called once from 950 `main'. 951 952`name' 953 This is the name of the current function. The index number is 954 repeated after it. 955 956 If the function is part of a cycle of recursion, the cycle number 957 is printed between the function's name and the index number (*note 958 How Mutually Recursive Functions Are Described: Cycles.). For 959 example, if function `gnurr' is part of cycle number one, and has 960 index number twelve, its primary line would be end like this: 961 962 gnurr <cycle 1> [12] 963 964 965File: gprof.info, Node: Callers, Next: Subroutines, Prev: Primary, Up: Call Graph 966 9675.2.2 Lines for a Function's Callers 968------------------------------------ 969 970A function's entry has a line for each function it was called by. 971These lines' fields correspond to the fields of the primary line, but 972their meanings are different because of the difference in context. 973 974 For reference, we repeat two lines from the entry for the function 975`report', the primary line and one caller-line preceding it, together 976with the heading line that shows the names of the fields: 977 978 index % time self children called name 979 ... 980 0.00 0.05 1/1 main [2] 981 [3] 100.0 0.00 0.05 1 report [3] 982 983 Here are the meanings of the fields in the caller-line for `report' 984called from `main': 985 986`self' 987 An estimate of the amount of time spent in `report' itself when it 988 was called from `main'. 989 990`children' 991 An estimate of the amount of time spent in subroutines of `report' 992 when `report' was called from `main'. 993 994 The sum of the `self' and `children' fields is an estimate of the 995 amount of time spent within calls to `report' from `main'. 996 997`called' 998 Two numbers: the number of times `report' was called from `main', 999 followed by the total number of non-recursive calls to `report' 1000 from all its callers. 1001 1002`name and index number' 1003 The name of the caller of `report' to which this line applies, 1004 followed by the caller's index number. 1005 1006 Not all functions have entries in the call graph; some options to 1007 `gprof' request the omission of certain functions. When a caller 1008 has no entry of its own, it still has caller-lines in the entries 1009 of the functions it calls. 1010 1011 If the caller is part of a recursion cycle, the cycle number is 1012 printed between the name and the index number. 1013 1014 If the identity of the callers of a function cannot be determined, a 1015dummy caller-line is printed which has `<spontaneous>' as the "caller's 1016name" and all other fields blank. This can happen for signal handlers. 1017 1018 1019File: gprof.info, Node: Subroutines, Next: Cycles, Prev: Callers, Up: Call Graph 1020 10215.2.3 Lines for a Function's Subroutines 1022---------------------------------------- 1023 1024A function's entry has a line for each of its subroutines--in other 1025words, a line for each other function that it called. These lines' 1026fields correspond to the fields of the primary line, but their meanings 1027are different because of the difference in context. 1028 1029 For reference, we repeat two lines from the entry for the function 1030`main', the primary line and a line for a subroutine, together with the 1031heading line that shows the names of the fields: 1032 1033 index % time self children called name 1034 ... 1035 [2] 100.0 0.00 0.05 1 main [2] 1036 0.00 0.05 1/1 report [3] 1037 1038 Here are the meanings of the fields in the subroutine-line for `main' 1039calling `report': 1040 1041`self' 1042 An estimate of the amount of time spent directly within `report' 1043 when `report' was called from `main'. 1044 1045`children' 1046 An estimate of the amount of time spent in subroutines of `report' 1047 when `report' was called from `main'. 1048 1049 The sum of the `self' and `children' fields is an estimate of the 1050 total time spent in calls to `report' from `main'. 1051 1052`called' 1053 Two numbers, the number of calls to `report' from `main' followed 1054 by the total number of non-recursive calls to `report'. This 1055 ratio is used to determine how much of `report''s `self' and 1056 `children' time gets credited to `main'. *Note Estimating 1057 `children' Times: Assumptions. 1058 1059`name' 1060 The name of the subroutine of `main' to which this line applies, 1061 followed by the subroutine's index number. 1062 1063 If the caller is part of a recursion cycle, the cycle number is 1064 printed between the name and the index number. 1065 1066 1067File: gprof.info, Node: Cycles, Prev: Subroutines, Up: Call Graph 1068 10695.2.4 How Mutually Recursive Functions Are Described 1070---------------------------------------------------- 1071 1072The graph may be complicated by the presence of "cycles of recursion" 1073in the call graph. A cycle exists if a function calls another function 1074that (directly or indirectly) calls (or appears to call) the original 1075function. For example: if `a' calls `b', and `b' calls `a', then `a' 1076and `b' form a cycle. 1077 1078 Whenever there are call paths both ways between a pair of functions, 1079they belong to the same cycle. If `a' and `b' call each other and `b' 1080and `c' call each other, all three make one cycle. Note that even if 1081`b' only calls `a' if it was not called from `a', `gprof' cannot 1082determine this, so `a' and `b' are still considered a cycle. 1083 1084 The cycles are numbered with consecutive integers. When a function 1085belongs to a cycle, each time the function name appears in the call 1086graph it is followed by `<cycle NUMBER>'. 1087 1088 The reason cycles matter is that they make the time values in the 1089call graph paradoxical. The "time spent in children" of `a' should 1090include the time spent in its subroutine `b' and in `b''s 1091subroutines--but one of `b''s subroutines is `a'! How much of `a''s 1092time should be included in the children of `a', when `a' is indirectly 1093recursive? 1094 1095 The way `gprof' resolves this paradox is by creating a single entry 1096for the cycle as a whole. The primary line of this entry describes the 1097total time spent directly in the functions of the cycle. The 1098"subroutines" of the cycle are the individual functions of the cycle, 1099and all other functions that were called directly by them. The 1100"callers" of the cycle are the functions, outside the cycle, that 1101called functions in the cycle. 1102 1103 Here is an example portion of a call graph which shows a cycle 1104containing functions `a' and `b'. The cycle was entered by a call to 1105`a' from `main'; both `a' and `b' called `c'. 1106 1107 index % time self children called name 1108 ---------------------------------------- 1109 1.77 0 1/1 main [2] 1110 [3] 91.71 1.77 0 1+5 <cycle 1 as a whole> [3] 1111 1.02 0 3 b <cycle 1> [4] 1112 0.75 0 2 a <cycle 1> [5] 1113 ---------------------------------------- 1114 3 a <cycle 1> [5] 1115 [4] 52.85 1.02 0 0 b <cycle 1> [4] 1116 2 a <cycle 1> [5] 1117 0 0 3/6 c [6] 1118 ---------------------------------------- 1119 1.77 0 1/1 main [2] 1120 2 b <cycle 1> [4] 1121 [5] 38.86 0.75 0 1 a <cycle 1> [5] 1122 3 b <cycle 1> [4] 1123 0 0 3/6 c [6] 1124 ---------------------------------------- 1125 1126(The entire call graph for this program contains in addition an entry 1127for `main', which calls `a', and an entry for `c', with callers `a' and 1128`b'.) 1129 1130 index % time self children called name 1131 <spontaneous> 1132 [1] 100.00 0 1.93 0 start [1] 1133 0.16 1.77 1/1 main [2] 1134 ---------------------------------------- 1135 0.16 1.77 1/1 start [1] 1136 [2] 100.00 0.16 1.77 1 main [2] 1137 1.77 0 1/1 a <cycle 1> [5] 1138 ---------------------------------------- 1139 1.77 0 1/1 main [2] 1140 [3] 91.71 1.77 0 1+5 <cycle 1 as a whole> [3] 1141 1.02 0 3 b <cycle 1> [4] 1142 0.75 0 2 a <cycle 1> [5] 1143 0 0 6/6 c [6] 1144 ---------------------------------------- 1145 3 a <cycle 1> [5] 1146 [4] 52.85 1.02 0 0 b <cycle 1> [4] 1147 2 a <cycle 1> [5] 1148 0 0 3/6 c [6] 1149 ---------------------------------------- 1150 1.77 0 1/1 main [2] 1151 2 b <cycle 1> [4] 1152 [5] 38.86 0.75 0 1 a <cycle 1> [5] 1153 3 b <cycle 1> [4] 1154 0 0 3/6 c [6] 1155 ---------------------------------------- 1156 0 0 3/6 b <cycle 1> [4] 1157 0 0 3/6 a <cycle 1> [5] 1158 [6] 0.00 0 0 6 c [6] 1159 ---------------------------------------- 1160 1161 The `self' field of the cycle's primary line is the total time spent 1162in all the functions of the cycle. It equals the sum of the `self' 1163fields for the individual functions in the cycle, found in the entry in 1164the subroutine lines for these functions. 1165 1166 The `children' fields of the cycle's primary line and subroutine 1167lines count only subroutines outside the cycle. Even though `a' calls 1168`b', the time spent in those calls to `b' is not counted in `a''s 1169`children' time. Thus, we do not encounter the problem of what to do 1170when the time in those calls to `b' includes indirect recursive calls 1171back to `a'. 1172 1173 The `children' field of a caller-line in the cycle's entry estimates 1174the amount of time spent _in the whole cycle_, and its other 1175subroutines, on the times when that caller called a function in the 1176cycle. 1177 1178 The `called' field in the primary line for the cycle has two numbers: 1179first, the number of times functions in the cycle were called by 1180functions outside the cycle; second, the number of times they were 1181called by functions in the cycle (including times when a function in 1182the cycle calls itself). This is a generalization of the usual split 1183into non-recursive and recursive calls. 1184 1185 The `called' field of a subroutine-line for a cycle member in the 1186cycle's entry says how many time that function was called from 1187functions in the cycle. The total of all these is the second number in 1188the primary line's `called' field. 1189 1190 In the individual entry for a function in a cycle, the other 1191functions in the same cycle can appear as subroutines and as callers. 1192These lines show how many times each function in the cycle called or 1193was called from each other function in the cycle. The `self' and 1194`children' fields in these lines are blank because of the difficulty of 1195defining meanings for them when recursion is going on. 1196 1197 1198File: gprof.info, Node: Line-by-line, Next: Annotated Source, Prev: Call Graph, Up: Output 1199 12005.3 Line-by-line Profiling 1201========================== 1202 1203`gprof''s `-l' option causes the program to perform "line-by-line" 1204profiling. In this mode, histogram samples are assigned not to 1205functions, but to individual lines of source code. This only works 1206with programs compiled with older versions of the `gcc' compiler. 1207Newer versions of `gcc' use a different program - `gcov' - to display 1208line-by-line profiling information. 1209 1210 With the older versions of `gcc' the program usually has to be 1211compiled with a `-g' option, in addition to `-pg', in order to generate 1212debugging symbols for tracking source code lines. Note, in much older 1213versions of `gcc' the program had to be compiled with the `-a' command 1214line option as well. 1215 1216 The flat profile is the most useful output table in line-by-line 1217mode. The call graph isn't as useful as normal, since the current 1218version of `gprof' does not propagate call graph arcs from source code 1219lines to the enclosing function. The call graph does, however, show 1220each line of code that called each function, along with a count. 1221 1222 Here is a section of `gprof''s output, without line-by-line 1223profiling. Note that `ct_init' accounted for four histogram hits, and 122413327 calls to `init_block'. 1225 1226 Flat profile: 1227 1228 Each sample counts as 0.01 seconds. 1229 % cumulative self self total 1230 time seconds seconds calls us/call us/call name 1231 30.77 0.13 0.04 6335 6.31 6.31 ct_init 1232 1233 1234 Call graph (explanation follows) 1235 1236 1237 granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds 1238 1239 index % time self children called name 1240 1241 0.00 0.00 1/13496 name_too_long 1242 0.00 0.00 40/13496 deflate 1243 0.00 0.00 128/13496 deflate_fast 1244 0.00 0.00 13327/13496 ct_init 1245 [7] 0.0 0.00 0.00 13496 init_block 1246 1247 Now let's look at some of `gprof''s output from the same program run, 1248this time with line-by-line profiling enabled. Note that `ct_init''s 1249four histogram hits are broken down into four lines of source code--one 1250hit occurred on each of lines 349, 351, 382 and 385. In the call graph, 1251note how `ct_init''s 13327 calls to `init_block' are broken down into 1252one call from line 396, 3071 calls from line 384, 3730 calls from line 1253385, and 6525 calls from 387. 1254 1255 Flat profile: 1256 1257 Each sample counts as 0.01 seconds. 1258 % cumulative self 1259 time seconds seconds calls name 1260 7.69 0.10 0.01 ct_init (trees.c:349) 1261 7.69 0.11 0.01 ct_init (trees.c:351) 1262 7.69 0.12 0.01 ct_init (trees.c:382) 1263 7.69 0.13 0.01 ct_init (trees.c:385) 1264 1265 1266 Call graph (explanation follows) 1267 1268 1269 granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds 1270 1271 % time self children called name 1272 1273 0.00 0.00 1/13496 name_too_long (gzip.c:1440) 1274 0.00 0.00 1/13496 deflate (deflate.c:763) 1275 0.00 0.00 1/13496 ct_init (trees.c:396) 1276 0.00 0.00 2/13496 deflate (deflate.c:727) 1277 0.00 0.00 4/13496 deflate (deflate.c:686) 1278 0.00 0.00 5/13496 deflate (deflate.c:675) 1279 0.00 0.00 12/13496 deflate (deflate.c:679) 1280 0.00 0.00 16/13496 deflate (deflate.c:730) 1281 0.00 0.00 128/13496 deflate_fast (deflate.c:654) 1282 0.00 0.00 3071/13496 ct_init (trees.c:384) 1283 0.00 0.00 3730/13496 ct_init (trees.c:385) 1284 0.00 0.00 6525/13496 ct_init (trees.c:387) 1285 [6] 0.0 0.00 0.00 13496 init_block (trees.c:408) 1286 1287 1288File: gprof.info, Node: Annotated Source, Prev: Line-by-line, Up: Output 1289 12905.4 The Annotated Source Listing 1291================================ 1292 1293`gprof''s `-A' option triggers an annotated source listing, which lists 1294the program's source code, each function labeled with the number of 1295times it was called. You may also need to specify the `-I' option, if 1296`gprof' can't find the source code files. 1297 1298 With older versions of `gcc' compiling with `gcc ... -g -pg -a' 1299augments your program with basic-block counting code, in addition to 1300function counting code. This enables `gprof' to determine how many 1301times each line of code was executed. With newer versions of `gcc' 1302support for displaying basic-block counts is provided by the `gcov' 1303program. 1304 1305 For example, consider the following function, taken from gzip, with 1306line numbers added: 1307 1308 1 ulg updcrc(s, n) 1309 2 uch *s; 1310 3 unsigned n; 1311 4 { 1312 5 register ulg c; 1313 6 1314 7 static ulg crc = (ulg)0xffffffffL; 1315 8 1316 9 if (s == NULL) { 1317 10 c = 0xffffffffL; 1318 11 } else { 1319 12 c = crc; 1320 13 if (n) do { 1321 14 c = crc_32_tab[...]; 1322 15 } while (--n); 1323 16 } 1324 17 crc = c; 1325 18 return c ^ 0xffffffffL; 1326 19 } 1327 1328 `updcrc' has at least five basic-blocks. One is the function 1329itself. The `if' statement on line 9 generates two more basic-blocks, 1330one for each branch of the `if'. A fourth basic-block results from the 1331`if' on line 13, and the contents of the `do' loop form the fifth 1332basic-block. The compiler may also generate additional basic-blocks to 1333handle various special cases. 1334 1335 A program augmented for basic-block counting can be analyzed with 1336`gprof -l -A'. The `-x' option is also helpful, to ensure that each 1337line of code is labeled at least once. Here is `updcrc''s annotated 1338source listing for a sample `gzip' run: 1339 1340 ulg updcrc(s, n) 1341 uch *s; 1342 unsigned n; 1343 2 ->{ 1344 register ulg c; 1345 1346 static ulg crc = (ulg)0xffffffffL; 1347 1348 2 -> if (s == NULL) { 1349 1 -> c = 0xffffffffL; 1350 1 -> } else { 1351 1 -> c = crc; 1352 1 -> if (n) do { 1353 26312 -> c = crc_32_tab[...]; 1354 26312,1,26311 -> } while (--n); 1355 } 1356 2 -> crc = c; 1357 2 -> return c ^ 0xffffffffL; 1358 2 ->} 1359 1360 In this example, the function was called twice, passing once through 1361each branch of the `if' statement. The body of the `do' loop was 1362executed a total of 26312 times. Note how the `while' statement is 1363annotated. It began execution 26312 times, once for each iteration 1364through the loop. One of those times (the last time) it exited, while 1365it branched back to the beginning of the loop 26311 times. 1366 1367 1368File: gprof.info, Node: Inaccuracy, Next: How do I?, Prev: Output, Up: Top 1369 13706 Inaccuracy of `gprof' Output 1371****************************** 1372 1373* Menu: 1374 1375* Sampling Error:: Statistical margins of error 1376* Assumptions:: Estimating children times 1377 1378 1379File: gprof.info, Node: Sampling Error, Next: Assumptions, Up: Inaccuracy 1380 13816.1 Statistical Sampling Error 1382============================== 1383 1384The run-time figures that `gprof' gives you are based on a sampling 1385process, so they are subject to statistical inaccuracy. If a function 1386runs only a small amount of time, so that on the average the sampling 1387process ought to catch that function in the act only once, there is a 1388pretty good chance it will actually find that function zero times, or 1389twice. 1390 1391 By contrast, the number-of-calls and basic-block figures are derived 1392by counting, not sampling. They are completely accurate and will not 1393vary from run to run if your program is deterministic and single 1394threaded. In multi-threaded applications, or single threaded 1395applications that link with multi-threaded libraries, the counts are 1396only deterministic if the counting function is thread-safe. (Note: 1397beware that the mcount counting function in glibc is _not_ 1398thread-safe). *Note Implementation of Profiling: Implementation. 1399 1400 The "sampling period" that is printed at the beginning of the flat 1401profile says how often samples are taken. The rule of thumb is that a 1402run-time figure is accurate if it is considerably bigger than the 1403sampling period. 1404 1405 The actual amount of error can be predicted. For N samples, the 1406_expected_ error is the square-root of N. For example, if the sampling 1407period is 0.01 seconds and `foo''s run-time is 1 second, N is 100 1408samples (1 second/0.01 seconds), sqrt(N) is 10 samples, so the expected 1409error in `foo''s run-time is 0.1 seconds (10*0.01 seconds), or ten 1410percent of the observed value. Again, if the sampling period is 0.01 1411seconds and `bar''s run-time is 100 seconds, N is 10000 samples, 1412sqrt(N) is 100 samples, so the expected error in `bar''s run-time is 1 1413second, or one percent of the observed value. It is likely to vary 1414this much _on the average_ from one profiling run to the next. 1415(_Sometimes_ it will vary more.) 1416 1417 This does not mean that a small run-time figure is devoid of 1418information. If the program's _total_ run-time is large, a small 1419run-time for one function does tell you that that function used an 1420insignificant fraction of the whole program's time. Usually this means 1421it is not worth optimizing. 1422 1423 One way to get more accuracy is to give your program more (but 1424similar) input data so it will take longer. Another way is to combine 1425the data from several runs, using the `-s' option of `gprof'. Here is 1426how: 1427 1428 1. Run your program once. 1429 1430 2. Issue the command `mv gmon.out gmon.sum'. 1431 1432 3. Run your program again, the same as before. 1433 1434 4. Merge the new data in `gmon.out' into `gmon.sum' with this command: 1435 1436 gprof -s EXECUTABLE-FILE gmon.out gmon.sum 1437 1438 5. Repeat the last two steps as often as you wish. 1439 1440 6. Analyze the cumulative data using this command: 1441 1442 gprof EXECUTABLE-FILE gmon.sum > OUTPUT-FILE 1443 1444 1445File: gprof.info, Node: Assumptions, Prev: Sampling Error, Up: Inaccuracy 1446 14476.2 Estimating `children' Times 1448=============================== 1449 1450Some of the figures in the call graph are estimates--for example, the 1451`children' time values and all the time figures in caller and 1452subroutine lines. 1453 1454 There is no direct information about these measurements in the 1455profile data itself. Instead, `gprof' estimates them by making an 1456assumption about your program that might or might not be true. 1457 1458 The assumption made is that the average time spent in each call to 1459any function `foo' is not correlated with who called `foo'. If `foo' 1460used 5 seconds in all, and 2/5 of the calls to `foo' came from `a', 1461then `foo' contributes 2 seconds to `a''s `children' time, by 1462assumption. 1463 1464 This assumption is usually true enough, but for some programs it is 1465far from true. Suppose that `foo' returns very quickly when its 1466argument is zero; suppose that `a' always passes zero as an argument, 1467while other callers of `foo' pass other arguments. In this program, 1468all the time spent in `foo' is in the calls from callers other than `a'. 1469But `gprof' has no way of knowing this; it will blindly and incorrectly 1470charge 2 seconds of time in `foo' to the children of `a'. 1471 1472 We hope some day to put more complete data into `gmon.out', so that 1473this assumption is no longer needed, if we can figure out how. For the 1474novice, the estimated figures are usually more useful than misleading. 1475 1476 1477File: gprof.info, Node: How do I?, Next: Incompatibilities, Prev: Inaccuracy, Up: Top 1478 14797 Answers to Common Questions 1480***************************** 1481 1482How can I get more exact information about hot spots in my program? 1483 Looking at the per-line call counts only tells part of the story. 1484 Because `gprof' can only report call times and counts by function, 1485 the best way to get finer-grained information on where the program 1486 is spending its time is to re-factor large functions into sequences 1487 of calls to smaller ones. Beware however that this can introduce 1488 artificial hot spots since compiling with `-pg' adds a significant 1489 overhead to function calls. An alternative solution is to use a 1490 non-intrusive profiler, e.g. oprofile. 1491 1492How do I find which lines in my program were executed the most times? 1493 Use the `gcov' program. 1494 1495How do I find which lines in my program called a particular function? 1496 Use `gprof -l' and lookup the function in the call graph. The 1497 callers will be broken down by function and line number. 1498 1499How do I analyze a program that runs for less than a second? 1500 Try using a shell script like this one: 1501 1502 for i in `seq 1 100`; do 1503 fastprog 1504 mv gmon.out gmon.out.$i 1505 done 1506 1507 gprof -s fastprog gmon.out.* 1508 1509 gprof fastprog gmon.sum 1510 1511 If your program is completely deterministic, all the call counts 1512 will be simple multiples of 100 (i.e., a function called once in 1513 each run will appear with a call count of 100). 1514 1515 1516 1517File: gprof.info, Node: Incompatibilities, Next: Details, Prev: How do I?, Up: Top 1518 15198 Incompatibilities with Unix `gprof' 1520************************************* 1521 1522GNU `gprof' and Berkeley Unix `gprof' use the same data file 1523`gmon.out', and provide essentially the same information. But there 1524are a few differences. 1525 1526 * GNU `gprof' uses a new, generalized file format with support for 1527 basic-block execution counts and non-realtime histograms. A magic 1528 cookie and version number allows `gprof' to easily identify new 1529 style files. Old BSD-style files can still be read. *Note 1530 Profiling Data File Format: File Format. 1531 1532 * For a recursive function, Unix `gprof' lists the function as a 1533 parent and as a child, with a `calls' field that lists the number 1534 of recursive calls. GNU `gprof' omits these lines and puts the 1535 number of recursive calls in the primary line. 1536 1537 * When a function is suppressed from the call graph with `-e', GNU 1538 `gprof' still lists it as a subroutine of functions that call it. 1539 1540 * GNU `gprof' accepts the `-k' with its argument in the form 1541 `from/to', instead of `from to'. 1542 1543 * In the annotated source listing, if there are multiple basic 1544 blocks on the same line, GNU `gprof' prints all of their counts, 1545 separated by commas. 1546 1547 * The blurbs, field widths, and output formats are different. GNU 1548 `gprof' prints blurbs after the tables, so that you can see the 1549 tables without skipping the blurbs. 1550 1551 1552File: gprof.info, Node: Details, Next: GNU Free Documentation License, Prev: Incompatibilities, Up: Top 1553 15549 Details of Profiling 1555********************** 1556 1557* Menu: 1558 1559* Implementation:: How a program collects profiling information 1560* File Format:: Format of `gmon.out' files 1561* Internals:: `gprof''s internal operation 1562* Debugging:: Using `gprof''s `-d' option 1563 1564 1565File: gprof.info, Node: Implementation, Next: File Format, Up: Details 1566 15679.1 Implementation of Profiling 1568=============================== 1569 1570Profiling works by changing how every function in your program is 1571compiled so that when it is called, it will stash away some information 1572about where it was called from. From this, the profiler can figure out 1573what function called it, and can count how many times it was called. 1574This change is made by the compiler when your program is compiled with 1575the `-pg' option, which causes every function to call `mcount' (or 1576`_mcount', or `__mcount', depending on the OS and compiler) as one of 1577its first operations. 1578 1579 The `mcount' routine, included in the profiling library, is 1580responsible for recording in an in-memory call graph table both its 1581parent routine (the child) and its parent's parent. This is typically 1582done by examining the stack frame to find both the address of the 1583child, and the return address in the original parent. Since this is a 1584very machine-dependent operation, `mcount' itself is typically a short 1585assembly-language stub routine that extracts the required information, 1586and then calls `__mcount_internal' (a normal C function) with two 1587arguments--`frompc' and `selfpc'. `__mcount_internal' is responsible 1588for maintaining the in-memory call graph, which records `frompc', 1589`selfpc', and the number of times each of these call arcs was traversed. 1590 1591 GCC Version 2 provides a magical function 1592(`__builtin_return_address'), which allows a generic `mcount' function 1593to extract the required information from the stack frame. However, on 1594some architectures, most notably the SPARC, using this builtin can be 1595very computationally expensive, and an assembly language version of 1596`mcount' is used for performance reasons. 1597 1598 Number-of-calls information for library routines is collected by 1599using a special version of the C library. The programs in it are the 1600same as in the usual C library, but they were compiled with `-pg'. If 1601you link your program with `gcc ... -pg', it automatically uses the 1602profiling version of the library. 1603 1604 Profiling also involves watching your program as it runs, and 1605keeping a histogram of where the program counter happens to be every 1606now and then. Typically the program counter is looked at around 100 1607times per second of run time, but the exact frequency may vary from 1608system to system. 1609 1610 This is done is one of two ways. Most UNIX-like operating systems 1611provide a `profil()' system call, which registers a memory array with 1612the kernel, along with a scale factor that determines how the program's 1613address space maps into the array. Typical scaling values cause every 16142 to 8 bytes of address space to map into a single array slot. On 1615every tick of the system clock (assuming the profiled program is 1616running), the value of the program counter is examined and the 1617corresponding slot in the memory array is incremented. Since this is 1618done in the kernel, which had to interrupt the process anyway to handle 1619the clock interrupt, very little additional system overhead is required. 1620 1621 However, some operating systems, most notably Linux 2.0 (and 1622earlier), do not provide a `profil()' system call. On such a system, 1623arrangements are made for the kernel to periodically deliver a signal 1624to the process (typically via `setitimer()'), which then performs the 1625same operation of examining the program counter and incrementing a slot 1626in the memory array. Since this method requires a signal to be 1627delivered to user space every time a sample is taken, it uses 1628considerably more overhead than kernel-based profiling. Also, due to 1629the added delay required to deliver the signal, this method is less 1630accurate as well. 1631 1632 A special startup routine allocates memory for the histogram and 1633either calls `profil()' or sets up a clock signal handler. This 1634routine (`monstartup') can be invoked in several ways. On Linux 1635systems, a special profiling startup file `gcrt0.o', which invokes 1636`monstartup' before `main', is used instead of the default `crt0.o'. 1637Use of this special startup file is one of the effects of using `gcc 1638... -pg' to link. On SPARC systems, no special startup files are used. 1639Rather, the `mcount' routine, when it is invoked for the first time 1640(typically when `main' is called), calls `monstartup'. 1641 1642 If the compiler's `-a' option was used, basic-block counting is also 1643enabled. Each object file is then compiled with a static array of 1644counts, initially zero. In the executable code, every time a new 1645basic-block begins (i.e., when an `if' statement appears), an extra 1646instruction is inserted to increment the corresponding count in the 1647array. At compile time, a paired array was constructed that recorded 1648the starting address of each basic-block. Taken together, the two 1649arrays record the starting address of every basic-block, along with the 1650number of times it was executed. 1651 1652 The profiling library also includes a function (`mcleanup') which is 1653typically registered using `atexit()' to be called as the program 1654exits, and is responsible for writing the file `gmon.out'. Profiling 1655is turned off, various headers are output, and the histogram is 1656written, followed by the call-graph arcs and the basic-block counts. 1657 1658 The output from `gprof' gives no indication of parts of your program 1659that are limited by I/O or swapping bandwidth. This is because samples 1660of the program counter are taken at fixed intervals of the program's 1661run time. Therefore, the time measurements in `gprof' output say 1662nothing about time that your program was not running. For example, a 1663part of the program that creates so much data that it cannot all fit in 1664physical memory at once may run very slowly due to thrashing, but 1665`gprof' will say it uses little time. On the other hand, sampling by 1666run time has the advantage that the amount of load due to other users 1667won't directly affect the output you get. 1668 1669 1670File: gprof.info, Node: File Format, Next: Internals, Prev: Implementation, Up: Details 1671 16729.2 Profiling Data File Format 1673============================== 1674 1675The old BSD-derived file format used for profile data does not contain a 1676magic cookie that allows to check whether a data file really is a 1677`gprof' file. Furthermore, it does not provide a version number, thus 1678rendering changes to the file format almost impossible. GNU `gprof' 1679uses a new file format that provides these features. For backward 1680compatibility, GNU `gprof' continues to support the old BSD-derived 1681format, but not all features are supported with it. For example, 1682basic-block execution counts cannot be accommodated by the old file 1683format. 1684 1685 The new file format is defined in header file `gmon_out.h'. It 1686consists of a header containing the magic cookie and a version number, 1687as well as some spare bytes available for future extensions. All data 1688in a profile data file is in the native format of the target for which 1689the profile was collected. GNU `gprof' adapts automatically to the 1690byte-order in use. 1691 1692 In the new file format, the header is followed by a sequence of 1693records. Currently, there are three different record types: histogram 1694records, call-graph arc records, and basic-block execution count 1695records. Each file can contain any number of each record type. When 1696reading a file, GNU `gprof' will ensure records of the same type are 1697compatible with each other and compute the union of all records. For 1698example, for basic-block execution counts, the union is simply the sum 1699of all execution counts for each basic-block. 1700 17019.2.1 Histogram Records 1702----------------------- 1703 1704Histogram records consist of a header that is followed by an array of 1705bins. The header contains the text-segment range that the histogram 1706spans, the size of the histogram in bytes (unlike in the old BSD 1707format, this does not include the size of the header), the rate of the 1708profiling clock, and the physical dimension that the bin counts 1709represent after being scaled by the profiling clock rate. The physical 1710dimension is specified in two parts: a long name of up to 15 characters 1711and a single character abbreviation. For example, a histogram 1712representing real-time would specify the long name as "seconds" and the 1713abbreviation as "s". This feature is useful for architectures that 1714support performance monitor hardware (which, fortunately, is becoming 1715increasingly common). For example, under DEC OSF/1, the "uprofile" 1716command can be used to produce a histogram of, say, instruction cache 1717misses. In this case, the dimension in the histogram header could be 1718set to "i-cache misses" and the abbreviation could be set to "1" 1719(because it is simply a count, not a physical dimension). Also, the 1720profiling rate would have to be set to 1 in this case. 1721 1722 Histogram bins are 16-bit numbers and each bin represent an equal 1723amount of text-space. For example, if the text-segment is one thousand 1724bytes long and if there are ten bins in the histogram, each bin 1725represents one hundred bytes. 1726 17279.2.2 Call-Graph Records 1728------------------------ 1729 1730Call-graph records have a format that is identical to the one used in 1731the BSD-derived file format. It consists of an arc in the call graph 1732and a count indicating the number of times the arc was traversed during 1733program execution. Arcs are specified by a pair of addresses: the 1734first must be within caller's function and the second must be within 1735the callee's function. When performing profiling at the function 1736level, these addresses can point anywhere within the respective 1737function. However, when profiling at the line-level, it is better if 1738the addresses are as close to the call-site/entry-point as possible. 1739This will ensure that the line-level call-graph is able to identify 1740exactly which line of source code performed calls to a function. 1741 17429.2.3 Basic-Block Execution Count Records 1743----------------------------------------- 1744 1745Basic-block execution count records consist of a header followed by a 1746sequence of address/count pairs. The header simply specifies the 1747length of the sequence. In an address/count pair, the address 1748identifies a basic-block and the count specifies the number of times 1749that basic-block was executed. Any address within the basic-address can 1750be used. 1751 1752 1753File: gprof.info, Node: Internals, Next: Debugging, Prev: File Format, Up: Details 1754 17559.3 `gprof''s Internal Operation 1756================================ 1757 1758Like most programs, `gprof' begins by processing its options. During 1759this stage, it may building its symspec list (`sym_ids.c:sym_id_add'), 1760if options are specified which use symspecs. `gprof' maintains a 1761single linked list of symspecs, which will eventually get turned into 176212 symbol tables, organized into six include/exclude pairs--one pair 1763each for the flat profile (INCL_FLAT/EXCL_FLAT), the call graph arcs 1764(INCL_ARCS/EXCL_ARCS), printing in the call graph 1765(INCL_GRAPH/EXCL_GRAPH), timing propagation in the call graph 1766(INCL_TIME/EXCL_TIME), the annotated source listing 1767(INCL_ANNO/EXCL_ANNO), and the execution count listing 1768(INCL_EXEC/EXCL_EXEC). 1769 1770 After option processing, `gprof' finishes building the symspec list 1771by adding all the symspecs in `default_excluded_list' to the exclude 1772lists EXCL_TIME and EXCL_GRAPH, and if line-by-line profiling is 1773specified, EXCL_FLAT as well. These default excludes are not added to 1774EXCL_ANNO, EXCL_ARCS, and EXCL_EXEC. 1775 1776 Next, the BFD library is called to open the object file, verify that 1777it is an object file, and read its symbol table (`core.c:core_init'), 1778using `bfd_canonicalize_symtab' after mallocing an appropriately sized 1779array of symbols. At this point, function mappings are read (if the 1780`--file-ordering' option has been specified), and the core text space 1781is read into memory (if the `-c' option was given). 1782 1783 `gprof''s own symbol table, an array of Sym structures, is now built. 1784This is done in one of two ways, by one of two routines, depending on 1785whether line-by-line profiling (`-l' option) has been enabled. For 1786normal profiling, the BFD canonical symbol table is scanned. For 1787line-by-line profiling, every text space address is examined, and a new 1788symbol table entry gets created every time the line number changes. In 1789either case, two passes are made through the symbol table--one to count 1790the size of the symbol table required, and the other to actually read 1791the symbols. In between the two passes, a single array of type `Sym' 1792is created of the appropriate length. Finally, 1793`symtab.c:symtab_finalize' is called to sort the symbol table and 1794remove duplicate entries (entries with the same memory address). 1795 1796 The symbol table must be a contiguous array for two reasons. First, 1797the `qsort' library function (which sorts an array) will be used to 1798sort the symbol table. Also, the symbol lookup routine 1799(`symtab.c:sym_lookup'), which finds symbols based on memory address, 1800uses a binary search algorithm which requires the symbol table to be a 1801sorted array. Function symbols are indicated with an `is_func' flag. 1802Line number symbols have no special flags set. Additionally, a symbol 1803can have an `is_static' flag to indicate that it is a local symbol. 1804 1805 With the symbol table read, the symspecs can now be translated into 1806Syms (`sym_ids.c:sym_id_parse'). Remember that a single symspec can 1807match multiple symbols. An array of symbol tables (`syms') is created, 1808each entry of which is a symbol table of Syms to be included or 1809excluded from a particular listing. The master symbol table and the 1810symspecs are examined by nested loops, and every symbol that matches a 1811symspec is inserted into the appropriate syms table. This is done 1812twice, once to count the size of each required symbol table, and again 1813to build the tables, which have been malloced between passes. From now 1814on, to determine whether a symbol is on an include or exclude symspec 1815list, `gprof' simply uses its standard symbol lookup routine on the 1816appropriate table in the `syms' array. 1817 1818 Now the profile data file(s) themselves are read 1819(`gmon_io.c:gmon_out_read'), first by checking for a new-style 1820`gmon.out' header, then assuming this is an old-style BSD `gmon.out' if 1821the magic number test failed. 1822 1823 New-style histogram records are read by `hist.c:hist_read_rec'. For 1824the first histogram record, allocate a memory array to hold all the 1825bins, and read them in. When multiple profile data files (or files 1826with multiple histogram records) are read, the memory ranges of each 1827pair of histogram records must be either equal, or non-overlapping. 1828For each pair of histogram records, the resolution (memory region size 1829divided by the number of bins) must be the same. The time unit must be 1830the same for all histogram records. If the above containts are met, all 1831histograms for the same memory range are merged. 1832 1833 As each call graph record is read (`call_graph.c:cg_read_rec'), the 1834parent and child addresses are matched to symbol table entries, and a 1835call graph arc is created by `cg_arcs.c:arc_add', unless the arc fails 1836a symspec check against INCL_ARCS/EXCL_ARCS. As each arc is added, a 1837linked list is maintained of the parent's child arcs, and of the child's 1838parent arcs. Both the child's call count and the arc's call count are 1839incremented by the record's call count. 1840 1841 Basic-block records are read (`basic_blocks.c:bb_read_rec'), but 1842only if line-by-line profiling has been selected. Each basic-block 1843address is matched to a corresponding line symbol in the symbol table, 1844and an entry made in the symbol's bb_addr and bb_calls arrays. Again, 1845if multiple basic-block records are present for the same address, the 1846call counts are cumulative. 1847 1848 A gmon.sum file is dumped, if requested (`gmon_io.c:gmon_out_write'). 1849 1850 If histograms were present in the data files, assign them to symbols 1851(`hist.c:hist_assign_samples') by iterating over all the sample bins 1852and assigning them to symbols. Since the symbol table is sorted in 1853order of ascending memory addresses, we can simple follow along in the 1854symbol table as we make our pass over the sample bins. This step 1855includes a symspec check against INCL_FLAT/EXCL_FLAT. Depending on the 1856histogram scale factor, a sample bin may span multiple symbols, in 1857which case a fraction of the sample count is allocated to each symbol, 1858proportional to the degree of overlap. This effect is rare for normal 1859profiling, but overlaps are more common during line-by-line profiling, 1860and can cause each of two adjacent lines to be credited with half a 1861hit, for example. 1862 1863 If call graph data is present, `cg_arcs.c:cg_assemble' is called. 1864First, if `-c' was specified, a machine-dependent routine (`find_call') 1865scans through each symbol's machine code, looking for subroutine call 1866instructions, and adding them to the call graph with a zero call count. 1867A topological sort is performed by depth-first numbering all the 1868symbols (`cg_dfn.c:cg_dfn'), so that children are always numbered less 1869than their parents, then making a array of pointers into the symbol 1870table and sorting it into numerical order, which is reverse topological 1871order (children appear before parents). Cycles are also detected at 1872this point, all members of which are assigned the same topological 1873number. Two passes are now made through this sorted array of symbol 1874pointers. The first pass, from end to beginning (parents to children), 1875computes the fraction of child time to propagate to each parent and a 1876print flag. The print flag reflects symspec handling of 1877INCL_GRAPH/EXCL_GRAPH, with a parent's include or exclude (print or no 1878print) property being propagated to its children, unless they 1879themselves explicitly appear in INCL_GRAPH or EXCL_GRAPH. A second 1880pass, from beginning to end (children to parents) actually propagates 1881the timings along the call graph, subject to a check against 1882INCL_TIME/EXCL_TIME. With the print flag, fractions, and timings now 1883stored in the symbol structures, the topological sort array is now 1884discarded, and a new array of pointers is assembled, this time sorted 1885by propagated time. 1886 1887 Finally, print the various outputs the user requested, which is now 1888fairly straightforward. The call graph (`cg_print.c:cg_print') and 1889flat profile (`hist.c:hist_print') are regurgitations of values already 1890computed. The annotated source listing 1891(`basic_blocks.c:print_annotated_source') uses basic-block information, 1892if present, to label each line of code with call counts, otherwise only 1893the function call counts are presented. 1894 1895 The function ordering code is marginally well documented in the 1896source code itself (`cg_print.c'). Basically, the functions with the 1897most use and the most parents are placed first, followed by other 1898functions with the most use, followed by lower use functions, followed 1899by unused functions at the end. 1900 1901 1902File: gprof.info, Node: Debugging, Prev: Internals, Up: Details 1903 19049.4 Debugging `gprof' 1905===================== 1906 1907If `gprof' was compiled with debugging enabled, the `-d' option 1908triggers debugging output (to stdout) which can be helpful in 1909understanding its operation. The debugging number specified is 1910interpreted as a sum of the following options: 1911 19122 - Topological sort 1913 Monitor depth-first numbering of symbols during call graph analysis 1914 19154 - Cycles 1916 Shows symbols as they are identified as cycle heads 1917 191816 - Tallying 1919 As the call graph arcs are read, show each arc and how the total 1920 calls to each function are tallied 1921 192232 - Call graph arc sorting 1923 Details sorting individual parents/children within each call graph 1924 entry 1925 192664 - Reading histogram and call graph records 1927 Shows address ranges of histograms as they are read, and each call 1928 graph arc 1929 1930128 - Symbol table 1931 Reading, classifying, and sorting the symbol table from the object 1932 file. For line-by-line profiling (`-l' option), also shows line 1933 numbers being assigned to memory addresses. 1934 1935256 - Static call graph 1936 Trace operation of `-c' option 1937 1938512 - Symbol table and arc table lookups 1939 Detail operation of lookup routines 1940 19411024 - Call graph propagation 1942 Shows how function times are propagated along the call graph 1943 19442048 - Basic-blocks 1945 Shows basic-block records as they are read from profile data (only 1946 meaningful with `-l' option) 1947 19484096 - Symspecs 1949 Shows symspec-to-symbol pattern matching operation 1950 19518192 - Annotate source 1952 Tracks operation of `-A' option 1953 1954 1955File: gprof.info, Node: GNU Free Documentation License, Prev: Details, Up: Top 1956 1957Appendix A GNU Free Documentation License 1958***************************************** 1959 1960 Version 1.3, 3 November 2008 1961 1962 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. 1963 `http://fsf.org/' 1964 1965 Everyone is permitted to copy and distribute verbatim copies 1966 of this license document, but changing it is not allowed. 1967 1968 0. PREAMBLE 1969 1970 The purpose of this License is to make a manual, textbook, or other 1971 functional and useful document "free" in the sense of freedom: to 1972 assure everyone the effective freedom to copy and redistribute it, 1973 with or without modifying it, either commercially or 1974 noncommercially. Secondarily, this License preserves for the 1975 author and publisher a way to get credit for their work, while not 1976 being considered responsible for modifications made by others. 1977 1978 This License is a kind of "copyleft", which means that derivative 1979 works of the document must themselves be free in the same sense. 1980 It complements the GNU General Public License, which is a copyleft 1981 license designed for free software. 1982 1983 We have designed this License in order to use it for manuals for 1984 free software, because free software needs free documentation: a 1985 free program should come with manuals providing the same freedoms 1986 that the software does. 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You 2001 accept the license if you copy, modify or distribute the work in a 2002 way requiring permission under copyright law. 2003 2004 A "Modified Version" of the Document means any work containing the 2005 Document or a portion of it, either copied verbatim, or with 2006 modifications and/or translated into another language. 2007 2008 A "Secondary Section" is a named appendix or a front-matter section 2009 of the Document that deals exclusively with the relationship of the 2010 publishers or authors of the Document to the Document's overall 2011 subject (or to related matters) and contains nothing that could 2012 fall directly within that overall subject. (Thus, if the Document 2013 is in part a textbook of mathematics, a Secondary Section may not 2014 explain any mathematics.) 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A 2030 Front-Cover Text may be at most 5 words, and a Back-Cover Text may 2031 be at most 25 words. 2032 2033 A "Transparent" copy of the Document means a machine-readable copy, 2034 represented in a format whose specification is available to the 2035 general public, that is suitable for revising the document 2036 straightforwardly with generic text editors or (for images 2037 composed of pixels) generic paint programs or (for drawings) some 2038 widely available drawing editor, and that is suitable for input to 2039 text formatters or for automatic translation to a variety of 2040 formats suitable for input to text formatters. A copy made in an 2041 otherwise Transparent file format whose markup, or absence of 2042 markup, has been arranged to thwart or discourage subsequent 2043 modification by readers is not Transparent. An image format is 2044 not Transparent if used for any substantial amount of text. A 2045 copy that is not "Transparent" is called "Opaque". 2046 2047 Examples of suitable formats for Transparent copies include plain 2048 ASCII without markup, Texinfo input format, LaTeX input format, 2049 SGML or XML using a publicly available DTD, and 2050 standard-conforming simple HTML, PostScript or PDF designed for 2051 human modification. Examples of transparent image formats include 2052 PNG, XCF and JPG. Opaque formats include proprietary formats that 2053 can be read and edited only by proprietary word processors, SGML or 2054 XML for which the DTD and/or processing tools are not generally 2055 available, and the machine-generated HTML, PostScript or PDF 2056 produced by some word processors for output purposes only. 2057 2058 The "Title Page" means, for a printed book, the title page itself, 2059 plus such following pages as are needed to hold, legibly, the 2060 material this License requires to appear in the title page. For 2061 works in formats which do not have any title page as such, "Title 2062 Page" means the text near the most prominent appearance of the 2063 work's title, preceding the beginning of the body of the text. 2064 2065 The "publisher" means any person or entity that distributes copies 2066 of the Document to the public. 2067 2068 A section "Entitled XYZ" means a named subunit of the Document 2069 whose title either is precisely XYZ or contains XYZ in parentheses 2070 following text that translates XYZ in another language. (Here XYZ 2071 stands for a specific section name mentioned below, such as 2072 "Acknowledgements", "Dedications", "Endorsements", or "History".) 2073 To "Preserve the Title" of such a section when you modify the 2074 Document means that it remains a section "Entitled XYZ" according 2075 to this definition. 2076 2077 The Document may include Warranty Disclaimers next to the notice 2078 which states that this License applies to the Document. These 2079 Warranty Disclaimers are considered to be included by reference in 2080 this License, but only as regards disclaiming warranties: any other 2081 implication that these Warranty Disclaimers may have is void and 2082 has no effect on the meaning of this License. 2083 2084 2. VERBATIM COPYING 2085 2086 You may copy and distribute the Document in any medium, either 2087 commercially or noncommercially, provided that this License, the 2088 copyright notices, and the license notice saying this License 2089 applies to the Document are reproduced in all copies, and that you 2090 add no other conditions whatsoever to those of this License. You 2091 may not use technical measures to obstruct or control the reading 2092 or further copying of the copies you make or distribute. However, 2093 you may accept compensation in exchange for copies. If you 2094 distribute a large enough number of copies you must also follow 2095 the conditions in section 3. 2096 2097 You may also lend copies, under the same conditions stated above, 2098 and you may publicly display copies. 2099 2100 3. COPYING IN QUANTITY 2101 2102 If you publish printed copies (or copies in media that commonly 2103 have printed covers) of the Document, numbering more than 100, and 2104 the Document's license notice requires Cover Texts, you must 2105 enclose the copies in covers that carry, clearly and legibly, all 2106 these Cover Texts: Front-Cover Texts on the front cover, and 2107 Back-Cover Texts on the back cover. Both covers must also clearly 2108 and legibly identify you as the publisher of these copies. The 2109 front cover must present the full title with all words of the 2110 title equally prominent and visible. You may add other material 2111 on the covers in addition. Copying with changes limited to the 2112 covers, as long as they preserve the title of the Document and 2113 satisfy these conditions, can be treated as verbatim copying in 2114 other respects. 2115 2116 If the required texts for either cover are too voluminous to fit 2117 legibly, you should put the first ones listed (as many as fit 2118 reasonably) on the actual cover, and continue the rest onto 2119 adjacent pages. 2120 2121 If you publish or distribute Opaque copies of the Document 2122 numbering more than 100, you must either include a 2123 machine-readable Transparent copy along with each Opaque copy, or 2124 state in or with each Opaque copy a computer-network location from 2125 which the general network-using public has access to download 2126 using public-standard network protocols a complete Transparent 2127 copy of the Document, free of added material. If you use the 2128 latter option, you must take reasonably prudent steps, when you 2129 begin distribution of Opaque copies in quantity, to ensure that 2130 this Transparent copy will remain thus accessible at the stated 2131 location until at least one year after the last time you 2132 distribute an Opaque copy (directly or through your agents or 2133 retailers) of that edition to the public. 2134 2135 It is requested, but not required, that you contact the authors of 2136 the Document well before redistributing any large number of 2137 copies, to give them a chance to provide you with an updated 2138 version of the Document. 2139 2140 4. MODIFICATIONS 2141 2142 You may copy and distribute a Modified Version of the Document 2143 under the conditions of sections 2 and 3 above, provided that you 2144 release the Modified Version under precisely this License, with 2145 the Modified Version filling the role of the Document, thus 2146 licensing distribution and modification of the Modified Version to 2147 whoever possesses a copy of it. In addition, you must do these 2148 things in the Modified Version: 2149 2150 A. Use in the Title Page (and on the covers, if any) a title 2151 distinct from that of the Document, and from those of 2152 previous versions (which should, if there were any, be listed 2153 in the History section of the Document). You may use the 2154 same title as a previous version if the original publisher of 2155 that version gives permission. 2156 2157 B. List on the Title Page, as authors, one or more persons or 2158 entities responsible for authorship of the modifications in 2159 the Modified Version, together with at least five of the 2160 principal authors of the Document (all of its principal 2161 authors, if it has fewer than five), unless they release you 2162 from this requirement. 2163 2164 C. State on the Title page the name of the publisher of the 2165 Modified Version, as the publisher. 2166 2167 D. Preserve all the copyright notices of the Document. 2168 2169 E. Add an appropriate copyright notice for your modifications 2170 adjacent to the other copyright notices. 2171 2172 F. Include, immediately after the copyright notices, a license 2173 notice giving the public permission to use the Modified 2174 Version under the terms of this License, in the form shown in 2175 the Addendum below. 2176 2177 G. Preserve in that license notice the full lists of Invariant 2178 Sections and required Cover Texts given in the Document's 2179 license notice. 2180 2181 H. Include an unaltered copy of this License. 2182 2183 I. Preserve the section Entitled "History", Preserve its Title, 2184 and add to it an item stating at least the title, year, new 2185 authors, and publisher of the Modified Version as given on 2186 the Title Page. If there is no section Entitled "History" in 2187 the Document, create one stating the title, year, authors, 2188 and publisher of the Document as given on its Title Page, 2189 then add an item describing the Modified Version as stated in 2190 the previous sentence. 2191 2192 J. Preserve the network location, if any, given in the Document 2193 for public access to a Transparent copy of the Document, and 2194 likewise the network locations given in the Document for 2195 previous versions it was based on. These may be placed in 2196 the "History" section. You may omit a network location for a 2197 work that was published at least four years before the 2198 Document itself, or if the original publisher of the version 2199 it refers to gives permission. 2200 2201 K. For any section Entitled "Acknowledgements" or "Dedications", 2202 Preserve the Title of the section, and preserve in the 2203 section all the substance and tone of each of the contributor 2204 acknowledgements and/or dedications given therein. 2205 2206 L. Preserve all the Invariant Sections of the Document, 2207 unaltered in their text and in their titles. Section numbers 2208 or the equivalent are not considered part of the section 2209 titles. 2210 2211 M. Delete any section Entitled "Endorsements". Such a section 2212 may not be included in the Modified Version. 2213 2214 N. Do not retitle any existing section to be Entitled 2215 "Endorsements" or to conflict in title with any Invariant 2216 Section. 2217 2218 O. Preserve any Warranty Disclaimers. 2219 2220 If the Modified Version includes new front-matter sections or 2221 appendices that qualify as Secondary Sections and contain no 2222 material copied from the Document, you may at your option 2223 designate some or all of these sections as invariant. To do this, 2224 add their titles to the list of Invariant Sections in the Modified 2225 Version's license notice. These titles must be distinct from any 2226 other section titles. 2227 2228 You may add a section Entitled "Endorsements", provided it contains 2229 nothing but endorsements of your Modified Version by various 2230 parties--for example, statements of peer review or that the text 2231 has been approved by an organization as the authoritative 2232 definition of a standard. 2233 2234 You may add a passage of up to five words as a Front-Cover Text, 2235 and a passage of up to 25 words as a Back-Cover Text, to the end 2236 of the list of Cover Texts in the Modified Version. Only one 2237 passage of Front-Cover Text and one of Back-Cover Text may be 2238 added by (or through arrangements made by) any one entity. If the 2239 Document already includes a cover text for the same cover, 2240 previously added by you or by arrangement made by the same entity 2241 you are acting on behalf of, you may not add another; but you may 2242 replace the old one, on explicit permission from the previous 2243 publisher that added the old one. 2244 2245 The author(s) and publisher(s) of the Document do not by this 2246 License give permission to use their names for publicity for or to 2247 assert or imply endorsement of any Modified Version. 2248 2249 5. COMBINING DOCUMENTS 2250 2251 You may combine the Document with other documents released under 2252 this License, under the terms defined in section 4 above for 2253 modified versions, provided that you include in the combination 2254 all of the Invariant Sections of all of the original documents, 2255 unmodified, and list them all as Invariant Sections of your 2256 combined work in its license notice, and that you preserve all 2257 their Warranty Disclaimers. 2258 2259 The combined work need only contain one copy of this License, and 2260 multiple identical Invariant Sections may be replaced with a single 2261 copy. If there are multiple Invariant Sections with the same name 2262 but different contents, make the title of each such section unique 2263 by adding at the end of it, in parentheses, the name of the 2264 original author or publisher of that section if known, or else a 2265 unique number. Make the same adjustment to the section titles in 2266 the list of Invariant Sections in the license notice of the 2267 combined work. 2268 2269 In the combination, you must combine any sections Entitled 2270 "History" in the various original documents, forming one section 2271 Entitled "History"; likewise combine any sections Entitled 2272 "Acknowledgements", and any sections Entitled "Dedications". You 2273 must delete all sections Entitled "Endorsements." 2274 2275 6. COLLECTIONS OF DOCUMENTS 2276 2277 You may make a collection consisting of the Document and other 2278 documents released under this License, and replace the individual 2279 copies of this License in the various documents with a single copy 2280 that is included in the collection, provided that you follow the 2281 rules of this License for verbatim copying of each of the 2282 documents in all other respects. 2283 2284 You may extract a single document from such a collection, and 2285 distribute it individually under this License, provided you insert 2286 a copy of this License into the extracted document, and follow 2287 this License in all other respects regarding verbatim copying of 2288 that document. 2289 2290 7. AGGREGATION WITH INDEPENDENT WORKS 2291 2292 A compilation of the Document or its derivatives with other 2293 separate and independent documents or works, in or on a volume of 2294 a storage or distribution medium, is called an "aggregate" if the 2295 copyright resulting from the compilation is not used to limit the 2296 legal rights of the compilation's users beyond what the individual 2297 works permit. When the Document is included in an aggregate, this 2298 License does not apply to the other works in the aggregate which 2299 are not themselves derivative works of the Document. 2300 2301 If the Cover Text requirement of section 3 is applicable to these 2302 copies of the Document, then if the Document is less than one half 2303 of the entire aggregate, the Document's Cover Texts may be placed 2304 on covers that bracket the Document within the aggregate, or the 2305 electronic equivalent of covers if the Document is in electronic 2306 form. Otherwise they must appear on printed covers that bracket 2307 the whole aggregate. 2308 2309 8. TRANSLATION 2310 2311 Translation is considered a kind of modification, so you may 2312 distribute translations of the Document under the terms of section 2313 4. Replacing Invariant Sections with translations requires special 2314 permission from their copyright holders, but you may include 2315 translations of some or all Invariant Sections in addition to the 2316 original versions of these Invariant Sections. You may include a 2317 translation of this License, and all the license notices in the 2318 Document, and any Warranty Disclaimers, provided that you also 2319 include the original English version of this License and the 2320 original versions of those notices and disclaimers. In case of a 2321 disagreement between the translation and the original version of 2322 this License or a notice or disclaimer, the original version will 2323 prevail. 2324 2325 If a section in the Document is Entitled "Acknowledgements", 2326 "Dedications", or "History", the requirement (section 4) to 2327 Preserve its Title (section 1) will typically require changing the 2328 actual title. 2329 2330 9. TERMINATION 2331 2332 You may not copy, modify, sublicense, or distribute the Document 2333 except as expressly provided under this License. Any attempt 2334 otherwise to copy, modify, sublicense, or distribute it is void, 2335 and will automatically terminate your rights under this License. 2336 2337 However, if you cease all violation of this License, then your 2338 license from a particular copyright holder is reinstated (a) 2339 provisionally, unless and until the copyright holder explicitly 2340 and finally terminates your license, and (b) permanently, if the 2341 copyright holder fails to notify you of the violation by some 2342 reasonable means prior to 60 days after the cessation. 2343 2344 Moreover, your license from a particular copyright holder is 2345 reinstated permanently if the copyright holder notifies you of the 2346 violation by some reasonable means, this is the first time you have 2347 received notice of violation of this License (for any work) from 2348 that copyright holder, and you cure the violation prior to 30 days 2349 after your receipt of the notice. 2350 2351 Termination of your rights under this section does not terminate 2352 the licenses of parties who have received copies or rights from 2353 you under this License. If your rights have been terminated and 2354 not permanently reinstated, receipt of a copy of some or all of 2355 the same material does not give you any rights to use it. 2356 2357 10. FUTURE REVISIONS OF THIS LICENSE 2358 2359 The Free Software Foundation may publish new, revised versions of 2360 the GNU Free Documentation License from time to time. Such new 2361 versions will be similar in spirit to the present version, but may 2362 differ in detail to address new problems or concerns. See 2363 `http://www.gnu.org/copyleft/'. 2364 2365 Each version of the License is given a distinguishing version 2366 number. If the Document specifies that a particular numbered 2367 version of this License "or any later version" applies to it, you 2368 have the option of following the terms and conditions either of 2369 that specified version or of any later version that has been 2370 published (not as a draft) by the Free Software Foundation. If 2371 the Document does not specify a version number of this License, 2372 you may choose any version ever published (not as a draft) by the 2373 Free Software Foundation. If the Document specifies that a proxy 2374 can decide which future versions of this License can be used, that 2375 proxy's public statement of acceptance of a version permanently 2376 authorizes you to choose that version for the Document. 2377 2378 11. RELICENSING 2379 2380 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any 2381 World Wide Web server that publishes copyrightable works and also 2382 provides prominent facilities for anybody to edit those works. A 2383 public wiki that anybody can edit is an example of such a server. 2384 A "Massive Multiauthor Collaboration" (or "MMC") contained in the 2385 site means any set of copyrightable works thus published on the MMC 2386 site. 2387 2388 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 2389 license published by Creative Commons Corporation, a not-for-profit 2390 corporation with a principal place of business in San Francisco, 2391 California, as well as future copyleft versions of that license 2392 published by that same organization. 2393 2394 "Incorporate" means to publish or republish a Document, in whole or 2395 in part, as part of another Document. 2396 2397 An MMC is "eligible for relicensing" if it is licensed under this 2398 License, and if all works that were first published under this 2399 License somewhere other than this MMC, and subsequently 2400 incorporated in whole or in part into the MMC, (1) had no cover 2401 texts or invariant sections, and (2) were thus incorporated prior 2402 to November 1, 2008. 2403 2404 The operator of an MMC Site may republish an MMC contained in the 2405 site under CC-BY-SA on the same site at any time before August 1, 2406 2009, provided the MMC is eligible for relicensing. 2407 2408 2409ADDENDUM: How to use this License for your documents 2410==================================================== 2411 2412To use this License in a document you have written, include a copy of 2413the License in the document and put the following copyright and license 2414notices just after the title page: 2415 2416 Copyright (C) YEAR YOUR NAME. 2417 Permission is granted to copy, distribute and/or modify this document 2418 under the terms of the GNU Free Documentation License, Version 1.3 2419 or any later version published by the Free Software Foundation; 2420 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover 2421 Texts. A copy of the license is included in the section entitled ``GNU 2422 Free Documentation License''. 2423 2424 If you have Invariant Sections, Front-Cover Texts and Back-Cover 2425Texts, replace the "with...Texts." line with this: 2426 2427 with the Invariant Sections being LIST THEIR TITLES, with 2428 the Front-Cover Texts being LIST, and with the Back-Cover Texts 2429 being LIST. 2430 2431 If you have Invariant Sections without Cover Texts, or some other 2432combination of the three, merge those two alternatives to suit the 2433situation. 2434 2435 If your document contains nontrivial examples of program code, we 2436recommend releasing these examples in parallel under your choice of 2437free software license, such as the GNU General Public License, to 2438permit their use in free software. 2439 2440 2441 2442Tag Table: 2443Node: Top777 2444Node: Introduction2103 2445Node: Compiling4595 2446Node: Executing8651 2447Node: Invoking11439 2448Node: Output Options12854 2449Node: Analysis Options19943 2450Node: Miscellaneous Options23641 2451Node: Deprecated Options24896 2452Node: Symspecs26965 2453Node: Output28791 2454Node: Flat Profile29831 2455Node: Call Graph34784 2456Node: Primary38016 2457Node: Callers40604 2458Node: Subroutines42721 2459Node: Cycles44562 2460Node: Line-by-line51339 2461Node: Annotated Source55412 2462Node: Inaccuracy58411 2463Node: Sampling Error58669 2464Node: Assumptions61573 2465Node: How do I?63043 2466Node: Incompatibilities64597 2467Node: Details66091 2468Node: Implementation66484 2469Node: File Format72381 2470Node: Internals76671 2471Node: Debugging85166 2472Node: GNU Free Documentation License86767 2473 2474End Tag Table 2475