This is gprof.info, produced by makeinfo version 4.8 from /home/xpgcust/tree/RI-2019.1/ib/p4root/Xtensa/Software/binutils/gprof/gprof.texi. 10/2018 Copyright (C) 1988, 1992, 1997, 1998, 1999, 2000, 2001, 2003, 2007, 2008, 2009 Free Software Foundation, Inc. Copyright (C) 1999-2009 Tensilica, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". This publication is provided "AS IS." Tensilica, Inc. (hereafter "Tensilica") does not make any warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. Information in this document is provided solely to enable system and software developers to use Tensilica(R) processors. Unless specifically set forth herein, there are no express or implied patent, copyright or any other intellectual property rights or licenses granted hereunder to design or fabricate Tensilica integrated circuits or integrated circuits based on the information in this document. Tensilica does not warrant that the contents of this publication, whether individually or as one or more groups, meets your requirements or that the publication is error-free. This publication could include technical inaccuracies or typographical errors. Changes may be made to the information herein, and these changes may be incorporated in new editions of this publication. The following terms are trademarks or registered trademarks of Tensilica, Inc.: FLIX, OSKit, Sea of Processors, Tensilica, Vectra, Xplorer, XPRES, and Xtensa. All other trademarks and registered trademarks are the property of their respective companies.  File: gprof.info, Node: Top, Next: Revisions, Up: (dir) GNU Profiler User's Guide ************************* This manual describes the GNU profiler, `gprof', and how you can use it to determine which parts of a program are taking most of the execution time. We assume that you know how to write, compile, and execute programs. GNU `gprof' was written by Jay Fenlason. This document is distributed under the terms of the GNU Free Documentation License version 1.3. A copy of the license is included in the section entitled "GNU Free Documentation License". * Menu: * Revisions:: Changes from previous versions. * Introduction:: What profiling means, and why it is useful. * Compiling:: How to compile your program for profiling. * Executing:: Executing your program to generate profile data * Invoking:: How to run `gprof', and its options * Output:: Interpreting `gprof''s output * Inaccuracy:: Potential problems you should be aware of * GNU Free Documentation License:: GNU Free Documentation License * History:: History of this document  File: gprof.info, Node: Revisions, Next: Introduction, Prev: Top, Up: Top Changes from Previous Versions ****************************** The following changes were made for version 14 of the Xtensa Tools: * Upgraded from version 2.18 to version 2.20 of the GNU Binary Utilities.  File: gprof.info, Node: Introduction, Next: Compiling, Prev: Revisions, Up: Top 1 Introduction to Profiling *************************** Profiling allows you to learn where your program spent its time and which functions called which other functions while it was executing. This information can show you which pieces of your program are slower than you expected, and might be candidates for rewriting to make your program execute faster. It can also tell you which functions are being called more or less often than you expected. This may help you spot bugs that had otherwise been unnoticed. Since the profiler uses information collected during the actual execution of your program, it can be used on programs that are too large or too complex to analyze by reading the source. However, how your program is run will affect the information that shows up in the profile data. If you don't use some feature of your program while it is being profiled, no profile information will be generated for that feature. Tensilica supports two options for collecting profile information. First, the Xtensa instruction set simulator (ISS) can directly generate the profile data. This is the easiest, most accurate, and most flexible option. If the profile data for your program needs to reflect interactions with real hardware, or if the ISS profiling is too slow, the second option is to profile your program running on a hardware implementation of your system. Hardware profiling requires certain Xtensa processor features, and it uses statistical sampling, which makes the results less accurate. Other profiling tools may be available from third-party operating system vendors. Profiling with the Xtensa ISS has several advantages over hardware profiling: * You do not need to compile the Xtensa program with special options (e.g., `-hwpg') before profiling it. * There is no instrumentation code added to the Xtensa program, so the profile results are not distorted by any extra code. * The Xtensa ISS can easily record the execution of every instruction, so there is no need to rely on statistical approximations like PC-sampling. * Instead of counting execution cycles, the Xtensa ISS can optionally record profile data for other events, such as cache misses. You can then use `xt-gprof' or Xplorer to view a profile of these other events. Hardware profiling also imposes certain requirements on your Xtensa system. The processor must include the Xtensa Debug Option, so that it can send the profile data back to a host system via the On-Chip Debugging (OCD) interface connected to the GNU Debugger (GDB). A dedicated Xtensa timer, preferably with a dedicated interrupt level, is required to control the PC sampling. For more information, please see the description of hardware profiling in the `Xtensa Software Development Toolkit User's Guide'. Regardless of whether you use the ISS or hardware profiling, Tensilica's `xt-gprof' uses a custom file format for the profile data. This allows profiling of discontiguous text regions and avoids inaccuracies related to combining the execution counts for adjacent instructions. Profiling has several steps: * You must compile and link your program. Depending on whether you are using the Xtensa ISS or hardware profiling, and depending on what `gprof' options you want to use, you may need to specify certain options to the compiler. *Note Compiling a Program for Profiling: Compiling. * You must execute your program to generate a profile data file. *Note Executing the Program: Executing. * You must run `xt-gprof' to analyze the profile data. *Note `gprof' Command Summary: Invoking. The next three chapters explain these steps in greater detail. The profile data files may contain several kinds of data. One section is a histogram of the events (cycle count, cache misses, etc.) for each Xtensa instruction. Another section records the execution count for each call-graph edge. The histogram counts and call-graph edge counts are read and analyzed by `gprof'. Several forms of output are available from the analysis. The "flat profile" shows the total histogram counts for each function, and how many times that function was called. If you simply want to know which functions have the highest counts (i.e., which functions burn most of the cycles, have the most cache misses, etc.), it is stated concisely here. *Note The Flat Profile: Flat Profile. The "call graph" shows, for each function, which functions called it, which other functions it called, and how many times. There is also an estimate of the histogram counts for the subroutines of each function. This can suggest places where you might try to eliminate function calls that use a lot of time. *Note The Call Graph: Call Graph. The "annotated source" listing is a copy of the program's source code, labeled with the number of times each line of the program was executed. *Note The Annotated Source Listing: Annotated Source.  File: gprof.info, Node: Compiling, Next: Executing, Prev: Introduction, Up: Top 2 Compiling a Program for Profiling *********************************** For profiling with the Xtensa ISS, nothing special is required when compiling your program. The profile data is collected by the ISS, so no instrumentation code needs to be added to your program. You may want to compile with `-g' to collect debugging information, which is used for line-by-line profiling. *Note Line-by-line Profiling: Line-by-line. For Tensilica's hardware profiling, the first step in generating profile information for your program is to compile and link it with profiling enabled. To compile a source file for profiling, specify the `-hwpg=N' option when you run the compiler, where N is the timer number used for profiling. (This is in addition to the options you normally use.) To link the program for profiling, use the XCC compiler to do the linking and simply specify `-hwpg=N' in addition to your usual options. The same option, `-hwpg', alters either compilation or linking to do what is necessary for profiling. Here are examples: xt-xcc -g -c myprog.c utils.c -hwpg=1 xt-xcc -o myprog myprog.o utils.o -hwpg=1 The `-hwpg' option also works with a command that both compiles and links: xt-xcc -o myprog myprog.c utils.c -g -hwpg=1 Note: If the `-hwpg' option is not part of your compilation options, but only your link options, you will avoid adding instrumentation code to your program, but no call-graph data will be gathered and when you run `gprof' you will get an error message like this: xt-gprof: gmon.out file is missing call-graph data If you add the `-Q' switch to suppress the printing of the call graph data you will still be able to see the time samples: Flat profile: self total cumulative self cycles cycles % cycles cycles calls /call /call name (K) (K) (K) (K) 44.12 7.69 7.69 zazLoop 35.29 13.84 6.15 main 20.59 17.42 3.59 bazMillion If you compile only some of the modules of the program with `-hwpg', you can still profile the program, but you won't get complete information about the modules that were compiled without `-hwpg'. The only information you get for the functions in those modules is the total time spent in them; there is no record of how many times they were called, or from where. This will not affect the flat profile (except that the `calls' field for the functions will be blank), but will greatly reduce the usefulness of the call graph. If you wish to perform line-by-line profiling, you will also need to specify the `-g' option, instructing the compiler to insert debugging symbols into the program that match program addresses to source code lines. *Note Line-by-line Profiling: Line-by-line.  File: gprof.info, Node: Executing, Next: Invoking, Prev: Compiling, Up: Top 3 Executing the Program *********************** Once the program is compiled, you must run it in order to generate the information that `gprof' needs. The way you run the program--the arguments and input that you give it--may have a dramatic effect on what the profile information shows. The profile data will describe the parts of the program that were activated for the particular input you use. For example, if the first command you give to your program is to quit, the profile data will show the time used in initialization and in cleanup, but not much else. * Menu: * Xtensa ISS:: Profiling with the Xtensa ISS * Xtensa Hardware:: Collecting profile data from Xtensa hardware  File: gprof.info, Node: Xtensa ISS, Next: Xtensa Hardware, Up: Executing 3.1 Profiling with the Xtensa ISS ================================= If you are profiling with the Xtensa instruction set simulator (ISS), you can specify two kinds of options to the ISS profiling client: * What events to profile: The default is to count the cycles spent executing each instruction, but you can also profile other events such as cache misses or pipeline interlocks. * The output file name: This is the raw data file to be read by `gprof'. If more than one kind of event is being profiled at the same time, the name you specify is used as the base name and the ISS appends a different suffix for each output file. For example, to profile instruction cache misses and write the results to a file named `misses.out', the ISS would be invoked with the `--client_cmds="profile --icmiss misses.out"' option. Please see the description of the `profile' client in the `Xtensa Instruction Set Simulator (ISS) User's Guide' for more information about these options. If you only want to profile cycle counts, you can simply invoke the ISS with the `--profile=OUTFILE' option. This is equivalent to `--client_cmds="profile OUTFILE"'. By default, `gprof' will expect the profile information to be in a file called `gmon.out'. Therefore, it is simplest to just use `--profile=gmon.out'. If your program runs for a long time and you want to use the fast functional simulation mode of the ISS (the `--turbo' option), you can still collect profile data. Nothing special is required to profile instruction counts (with `--client_cmds="profile --instructions"') in this mode. Other kinds of profile data require statistical sampling, using the `--sample' ISS option to periodically switch to the cycle-accurate simulation mode. You can specify the `--sample_insns' and `--sample_ratio' ISS options to control the size and frequency of the cycle-accurate samples. The sampled results are automatically extrapolated by the ISS to the fast functional portions of the simulation. See the `Xtensa Instruction Set Simulator (ISS) User's Guide' for more information. Depending on the kinds of events you want to profile, you may need to specify other ISS options. By default, the Xtensa ISS does not simulate the memory system; all memory references are assumed to be in cache. Use the `--mem_model' option if you want the cycle counts to reflect the effects of caches and local memory. If you are profiling cache misses, you will also need to use the `--mem_model' option.  File: gprof.info, Node: Xtensa Hardware, Prev: Xtensa ISS, Up: Executing 3.2 Xtensa Hardware Profiling ============================= After compiling your program for hardware profiling, run it on the hardware as you would normally debug it, using either `xt-gdb' or `xplorer --debug'. When your program calls `exit', the debugger will write the profile data to a file with a name composed of `gmon.out' followed by a unique suffix. If your program does not call `exit', you can interrupt it and use the debugger to call the `xt_profile_save_and_reset' function, which will write out the profile data. You can exit from the debugger after the profile data has been written out. See the `Xtensa Software Development Toolkit User's Guide' for details on using hardware profiling.  File: gprof.info, Node: Invoking, Next: Output, Prev: Executing, Up: Top 4 `gprof' Command Summary ************************* After you have a profile data file `gmon.out', you can run `gprof' to interpret the information in it. The `gprof' program prints a flat profile and a call graph on standard output. Typically you would redirect the output of `gprof' into a file with `>'. You run `gprof' like this: xt-gprof OPTIONS [EXECUTABLE-FILE [PROFILE-DATA-FILES...]] [> OUTFILE] Here square-brackets indicate optional arguments. If you omit the executable file name, the file `a.out' is used. If you give no profile data file name, the file `gmon.out' is used. If any file is not in the proper format, or if the profile data file does not appear to belong to the executable file, an error message is printed. You can give more than one profile data file by entering all their names after the executable file name; then the statistics in all the data files are summed together. The order of these options does not matter. * Menu: * Output Options:: Controlling `gprof''s output style * Analysis Options:: Controlling how `gprof' analyzes its data * Miscellaneous Options:: * Symspecs:: Specifying functions to include or exclude  File: gprof.info, Node: Output Options, Next: Analysis Options, Up: Invoking 4.1 Output Options ================== These options specify which of several output formats `gprof' should produce. Many of these options take an optional "symspec" to specify functions to be included or excluded. These options can be specified multiple times, with different symspecs, to include or exclude sets of symbols. *Note Symspecs: Symspecs. Specifying any of these options overrides the default (`-p -q'), which prints a flat profile and call graph analysis for all functions. `-A[SYMSPEC]' `--annotated-source[=SYMSPEC]' The `-A' option causes `gprof' to print annotated source code. If SYMSPEC is specified, print output only for matching symbols. *Note The Annotated Source Listing: Annotated Source. `-b' `--brief' If the `-b' option is given, `gprof' doesn't print the verbose blurbs that try to explain the meaning of all of the fields in the tables. This is useful if you intend to print out the output, or are tired of seeing the blurbs. `-C[SYMSPEC]' `--exec-counts[=SYMSPEC]' The `-C' option causes `gprof' to print a tally of functions and the number of times each was called. If SYMSPEC is specified, print tally only for matching symbols. If you profile instruction counts (not cycles) with the Xtensa ISS, that is, if you run ISS with `--client_cmds="profile --instructions"', invoking `gprof' with the `-l' option, along with `-C', will cause basic-block execution counts to be tallied and displayed. `-i' `--file-info' The `-i' option causes `gprof' to display summary information about the profile data file(s) and then exit. The number of histogram, call graph, and basic-block count records is displayed. `-I DIRS' `--directory-path=DIRS' The `-I' option specifies a list of search directories in which to find source files. Environment variable GPROF_PATH can also be used to convey this information. Used mostly for annotated source output. `-J[SYMSPEC]' `--no-annotated-source[=SYMSPEC]' The `-J' option causes `gprof' not to print annotated source code. If SYMSPEC is specified, `gprof' prints annotated source, but excludes matching symbols. `-L' `--print-path' Normally, source filenames are printed with the path component suppressed. The `-L' option causes `gprof' to print the full pathname of source filenames, which is determined from symbolic debugging information in the image file and is relative to the directory in which the compiler was invoked. `-p[SYMSPEC]' `--flat-profile[=SYMSPEC]' The `-p' option causes `gprof' to print a flat profile. If SYMSPEC is specified, print flat profile only for matching symbols. *Note The Flat Profile: Flat Profile. `-P[SYMSPEC]' `--no-flat-profile[=SYMSPEC]' The `-P' option causes `gprof' to suppress printing a flat profile. If SYMSPEC is specified, `gprof' prints a flat profile, but excludes matching symbols. `-q[SYMSPEC]' `--graph[=SYMSPEC]' The `-q' option causes `gprof' to print the call graph analysis. If SYMSPEC is specified, print call graph only for matching symbols and their children. *Note The Call Graph: Call Graph. `-Q[SYMSPEC]' `--no-graph[=SYMSPEC]' The `-Q' option causes `gprof' to suppress printing the call graph. If SYMSPEC is specified, `gprof' prints a call graph, but excludes matching symbols. `-t' `--table-length=NUM' The `-t' option causes the NUM most active source lines in each source file to be listed when source annotation is enabled. The default is 10. `-y' `--separate-files' This option affects annotated source output only. Normally, `gprof' prints annotated source files to standard-output. If this option is specified, annotated source for a file named `path/FILENAME' is generated in the file `FILENAME-ann'. If the underlying file system would truncate `FILENAME-ann' so that it overwrites the original `FILENAME', `gprof' generates annotated source in the file `FILENAME.ann' instead (if the original file name has an extension, that extension is _replaced_ with `.ann'). `-Z[SYMSPEC]' `--no-exec-counts[=SYMSPEC]' The `-Z' option causes `gprof' not to print a tally of functions and the number of times each was called. If SYMSPEC is specified, print tally, but exclude matching symbols. `-r' `--function-ordering' The `--function-ordering' option causes `gprof' to print a suggested function ordering for the program based on profiling data. This option suggests an ordering which may improve paging, tlb and cache behavior for the program on systems which support arbitrary ordering of functions in an executable. The exact details of how to force the linker to place functions in a particular order is system dependent and out of the scope of this manual. `-R MAP_FILE' `--file-ordering MAP_FILE' The `--file-ordering' option causes `gprof' to print a suggested .o link line ordering for the program based on profiling data. This option suggests an ordering which may improve paging, tlb and cache behavior for the program on systems which do not support arbitrary ordering of functions in an executable. Use of the `-a' argument is highly recommended with this option. The MAP_FILE argument is a pathname to a file which provides function name to object file mappings. The format of the file is similar to the output of the program `nm'. c-parse.o:00000000 T yyparse c-parse.o:00000004 C yyerrflag c-lang.o:00000000 T maybe_objc_method_name c-lang.o:00000000 T print_lang_statistics c-lang.o:00000000 T recognize_objc_keyword c-decl.o:00000000 T print_lang_identifier c-decl.o:00000000 T print_lang_type ... To create a MAP_FILE with GNU `nm', type a command like `nm --extern-only --defined-only -v --print-file-name program-name'. `-T' `--traditional' The `-T' option causes `gprof' to print its output in "traditional" BSD style. `-w WIDTH' `--width=WIDTH' Sets width of output lines to WIDTH. Currently only used when printing the function index at the bottom of the call graph. `-x' `--all-lines' This option affects annotated source output only. By default, only the lines at the beginning of a basic-block are annotated. If this option is specified, every line in a basic-block is annotated by repeating the annotation for the first line. This behavior is similar to `tcov''s `-a'. `--demangle[=STYLE]' `--no-demangle' These options control whether C++ symbol names should be demangled when printing output. The default is to demangle symbols. The `--no-demangle' option may be used to turn off demangling. Different compilers have different mangling styles. The optional demangling style argument can be used to choose an appropriate demangling style for your compiler.  File: gprof.info, Node: Analysis Options, Next: Miscellaneous Options, Prev: Output Options, Up: Invoking 4.2 Analysis Options ==================== `-a' `--no-static' The `-a' option causes `gprof' to suppress the printing of statically declared (private) functions. (These are functions whose names are not listed as global, and which are not visible outside the file/function/block where they were defined.) Time spent in these functions, calls to/from them, etc., will all be attributed to the function that was loaded directly before it in the executable file. This option affects both the flat profile and the call graph. `-c' `--static-call-graph' The `-c' option causes the call graph of the program to be augmented by a heuristic which examines the text space of the object file and identifies function calls in the binary machine code. Since normal call graph records are only generated when functions are entered, this option identifies children that could have been called, but never were. Calls to functions that were not compiled with profiling enabled are also identified, but only if symbol table entries are present for them. Calls to dynamic library routines are typically _not_ found by this option. Parents or children identified via this heuristic are indicated in the call graph with call counts of `0'. `-D' `--ignore-non-functions' The `-D' option causes `gprof' to ignore symbols which are not known to be functions. This option will give more accurate profile data on systems where it is supported (Solaris and HPUX for example). `-f' `--function-line' The `-f' option enables line-by-line profiling where all the lines for a function are grouped together in the flat profile. Specifically, the flat profile entries are first sorted by function in decreasing order of the histogram counts for the function as a whole, and then sorted by line within each function, again in decreasing order of histogram counts. Aside from the order of the flat profile entries, this option is the same as the `-l' option. The program must be compiled with a `-g' option so that line number information is available. `-k FROM/TO' The `-k' option allows you to delete from the call graph any arcs from symbols matching symspec FROM to those matching symspec TO. `-K LOWPC:HIGHPC' `--pc-range LOWPC:HIGHPC' The `-K' option allows you to exclude profile data outside a specific range of code. Histogram hits and call graph arcs with addresses lower than LOWPC or higher than HIGHPC are simply ignored. The addresses may be specified as decimal, hexadecimal or octal values, with a `0' prefix for octal values or a `0x' prefix for hexadecimal values. This option may be useful when analyzing the performance of a region of code that would otherwise be obscured by the rest of the program. `-l' `--line' The `-l' option enables line-by-line profiling, which causes histogram counts to be charged to individual source code lines, instead of functions. If you profile instruction counts (not cycles) with the Xtensa ISS, that is, if you run ISS with `--client_cmds="profile --instructions"', this option will also identify how many times each line of code was executed. The program must be compiled with a `-g' option so that line number information is available. While line-by-line profiling can help isolate where in a large function a program is spending its time, it also significantly increases the running time of `gprof', and magnifies statistical inaccuracies for hardware profiling. *Note Statistical Sampling Error: Sampling Error. `-m NUM' `--min-count=NUM' This option affects execution count output only. Symbols that are executed less than NUM times are suppressed. `-nSYMSPEC' `--time=SYMSPEC' The `-n' option causes `gprof', in its call graph analysis, to only propagate times for symbols matching SYMSPEC. `-NSYMSPEC' `--no-time=SYMSPEC' The `-n' option causes `gprof', in its call graph analysis, not to propagate times for symbols matching SYMSPEC. `-SFILENAME' `--external-symbol-table=FILENAME' The `-S' option causes `gprof' to read an external symbol table file, such as `/proc/kallsyms', rather than read the symbol table from the given object file (the default is `a.out'). This is useful for profiling kernel modules. `-z' `--display-unused-functions' If you give the `-z' option, `gprof' will mention all functions in the flat profile, even those that were never called, and that had no time spent in them. This is useful in conjunction with the `-c' option for discovering which routines were never called.  File: gprof.info, Node: Miscellaneous Options, Next: Symspecs, Prev: Analysis Options, Up: Invoking 4.3 Miscellaneous Options ========================= `-d[NUM]' `--debug[=NUM]' The `-d NUM' option specifies debugging options. If NUM is not specified, enable all debugging. `-h' `--help' The `-h' option prints command line usage. `-ONAME' `--file-format=NAME' Selects the format of the profile data files. Recognized formats are `auto' (the default), `bsd', `4.4bsd', `magic', and `prof' (not yet supported). `-s' `--sum' The `-s' option causes `gprof' to summarize the information in the profile data files it read in, and write out a profile data file called `gmon.sum', which contains all the information from the profile data files that `gprof' read in. The file `gmon.sum' may be one of the specified input files; the effect of this is to merge the data in the other input files into `gmon.sum'. Eventually you can run `gprof' again without `-s' to analyze the cumulative data in the file `gmon.sum'. `-v' `--version' The `-v' flag causes `gprof' to print the current version number, and then exit.  File: gprof.info, Node: Symspecs, Prev: Miscellaneous Options, Up: Invoking 4.4 Symspecs ============ Many of the output options allow functions to be included or excluded using "symspecs" (symbol specifications), which observe the following syntax: filename_containing_a_dot | funcname_not_containing_a_dot | linenumber | ( [ any_filename ] `:' ( any_funcname | linenumber ) ) Here are some sample symspecs: `main.c' Selects everything in file `main.c'--the dot in the string tells `gprof' to interpret the string as a filename, rather than as a function name. To select a file whose name does not contain a dot, a trailing colon should be specified. For example, `odd:' is interpreted as the file named `odd'. `main' Selects all functions named `main'. Note that there may be multiple instances of the same function name because some of the definitions may be local (i.e., static). Unless a function name is unique in a program, you must use the colon notation explained below to specify a function from a specific source file. Sometimes, function names contain dots. In such cases, it is necessary to add a leading colon to the name. For example, `:.mul' selects function `.mul'. In some object file formats, symbols have a leading underscore. `gprof' will normally not print these underscores. When you name a symbol in a symspec, you should type it exactly as `gprof' prints it in its output. For example, if the compiler produces a symbol `_main' from your `main' function, `gprof' still prints it as `main' in its output, so you should use `main' in symspecs. `main.c:main' Selects function `main' in file `main.c'. `main.c:134' Selects line 134 in file `main.c'.  File: gprof.info, Node: Output, Next: Inaccuracy, Prev: Invoking, Up: Top 5 Interpreting `gprof''s Output ******************************* `gprof' can produce several different output styles, the most important of which are described below. The simplest output styles (file information, execution count, and function and file ordering) are not described here, but are documented with the respective options that trigger them. *Note Output Options: Output Options. * Menu: * Flat Profile:: The flat profile shows how much time was spent executing directly in each function. * Call Graph:: The call graph shows which functions called which others, and how much time each function used when its subroutine calls are included. * Line-by-line:: `gprof' can analyze individual source code lines * Annotated Source:: The annotated source listing displays source code labeled with execution counts * Other Events:: Profiling events other than cycle counts.  File: gprof.info, Node: Flat Profile, Next: Call Graph, Up: Output 5.1 The Flat Profile ==================== The "flat profile" shows the total histogram counts for each function. Unless the `-z' option is given, functions with no apparent counts and no apparent calls to them, are not mentioned. Note that for hardware profiling if a function was not compiled for profiling, and didn't run long enough to show up on the program counter histogram, it will be indistinguishable from a function that was never called. Also, if the compiler optimizes a function call by inlining the function body, then the function call will not be counted and the time spent in the inlined function will be attributed to the caller. Line-by-line profiling may be helpful in revealing the effects of inlined functions. *Note Line-by-line Profiling: Line-by-line. This is part of a flat profile for a small program: Flat profile: Each sample counts as 16384 cycles. self total cumulative self cycles cycles % cycles cycles calls /call /call name (K) (K) (K) (K) 66.67 49.15 49.15 7208 0.01 0.01 open 16.67 65.54 16.38 244 0.07 0.20 offtime 16.67 81.92 16.38 8 2.05 2.05 memccpy 16.67 98.30 16.38 7 2.34 2.34 write 0.00 98.30 0.00 236 0.00 0.00 tzset 0.00 98.30 0.00 192 0.00 0.00 tolower 0.00 98.30 0.00 47 0.00 0.00 strlen 0.00 98.30 0.00 45 0.00 0.00 strchr 0.00 98.30 0.00 1 0.00 98.30 main 0.00 98.30 0.00 1 0.00 0.00 memcpy 0.00 98.30 0.00 1 0.00 16.38 print 0.00 98.30 0.00 1 0.00 98.30 report ... The functions are sorted first by decreasing run-time spent in them, then by decreasing number of calls, then alphabetically by name. `gprof' attempts to scale results so that the tables contain numbers of reasonable magnitude. If the counts are scaled, the scaling factor is shown at the top of the scaled columns. "T" indicates that the values are in units of trillions; "G" indicates billions; "M" indicates millions; and "K" indicates thousands. For hardware profiling, where the profile data is sampled, you must be careful interpreting the `gprof' results. Just before the column headers, a statement appears indicating how many units each sample counted as. This "sampling period" estimates the margin of error in each of the figures. A figure that is not much larger than this is not reliable. In this example, each sample counted as 16,384 cycles. The program's total execution time was 98.30 Kcycles, as indicated by the `cumulative cycles' field. Since each sample counted for 16,384 seconds, this means only six samples were taken during the run. Three of the samples occurred while the program was in the `open' function, as indicated by the `self cycles' field. Each of the other three samples occurred once each in `offtime', `memccpy', and `write'. Since only six samples were taken, none of these values can be regarded as particularly reliable. In another run, the `self cycles' field for `memccpy' might well be `0.00' or `32.77'. *Note Statistical Sampling Error: Sampling Error, for a complete discussion. The remaining functions in the listing (those whose `self cycles' field is `0.00') didn't appear in the histogram samples at all. However, the call graph indicated that they were called, so therefore they are listed, sorted in decreasing order by the `calls' field. Clearly some time was spent executing these functions, but the paucity of histogram samples prevents any determination of how much time each took. Here is what the fields in each line mean (the UNITS depend on the events being profiled, e.g., cycles, interlocks, etc.): `%' This is the percentage of the total histogram counts that are attributed to this function. These should all add up to 100%. `cumulative UNITS' This is the cumulative total number of UNITS the computer spent executing this function, plus the time spent in all the functions above this one in this table. `self UNITS' This is the number of UNITS accounted for by this function alone. The flat profile listing is sorted first by this number. `calls' This is the total number of times the function was called. `self UNITS/call' This represents the average number of UNITS spent in this function per call. `total UNITS/call' This represents the average number of UNITS spent in this function and its descendants per call. This is the only field in the flat profile that uses call graph analysis. `name' This is the name of the function. The flat profile is sorted by this field alphabetically after the "self UNITS" and "calls" fields are sorted.  File: gprof.info, Node: Call Graph, Next: Line-by-line, Prev: Flat Profile, Up: Output 5.2 The Call Graph ================== The "call graph" shows how much time was spent in each function and its children. From this information, you can find functions that, while they themselves may not have used much time, called other functions that did use unusual amounts of time. Note that in the same way as the flat profile, a function call inlined by the compiler will not be visible in the call graph and the counts for the inlined function will be attributed to the caller. Here is a sample call from a small program. This call came from the same `gprof' run as the flat profile example in the previous section. index % self children called name (K) (K) [1] 100.0 0.00 98.30 _start [1] 0.00 98.30 1/1 main [2] 0.00 0.00 1/2 _atexit [28] 0.00 0.00 1/1 exit [59] ----------------------------------------------- 0.00 98.30 1/1 _start [1] [2] 100.0 0.00 98.30 1 main [2] 0.00 98.30 1/1 report [3] ----------------------------------------------- 0.00 98.30 1/1 main [2] [3] 100.0 0.00 98.30 1 report [3] 0.00 49.15 8/8 timelocal [6] 0.00 16.38 1/1 print [9] 0.00 16.38 9/9 fgets [12] 0.00 0.00 12/34 strncmp [40] 0.00 0.00 8/8 lookup [20] 0.00 0.00 1/1 fopen [21] 0.00 0.00 8/8 chewtime [24] 0.00 0.00 8/16 skipspace [44] ----------------------------------------------- [4] 60.5 16.38 49.15 8+472 [4] 16.38 49.15 244+260 offtime [7] 0.00 0.00 236+1 tzset [26] ----------------------------------------------- As with the flat profile, `gprof' attempts to scale results so that the tables contain numbers of reasonable magnitude. If the counts are scaled, the scaling factor is shown at the top of the scaled columns. "T" indicates that the values are in units of trillions; "G" indicates billions; "M" indicates millions; and "K" indicates thousands. The lines full of dashes divide this table into "entries", one for each function. Each entry has one or more lines. In each entry, the primary line is the one that starts with an index number in square brackets. The end of this line says which function the entry is for. The preceding lines in the entry describe the callers of this function and the following lines describe its subroutines (also called "children" when we speak of the call graph). The entries are sorted by time spent in the function and its subroutines. * Menu: * Primary:: Details of the primary line's contents. * Callers:: Details of caller-lines' contents. * Subroutines:: Details of subroutine-lines' contents. * Cycles:: When there are cycles of recursion, such as `a' calls `b' calls `a'...  File: gprof.info, Node: Primary, Next: Callers, Up: Call Graph 5.2.1 The Primary Line ---------------------- The "primary line" in a call graph entry is the line that describes the function which the entry is about and gives the overall statistics for this function. For reference, we repeat the primary line from the entry for function `report' in our main example, together with the heading line that shows the names of the fields: index % self children called name ... [3] 100.0 0.00 98.30 1 report [3] Here is what the fields in the primary line mean: `index' Entries are numbered with consecutive integers. Each function therefore has an index number, which appears at the beginning of its primary line. Each cross-reference to a function, as a caller or subroutine of another, gives its index number as well as its name. The index number guides you if you wish to look for the entry for that function. `%' This is the percentage of the total histogram counts that were attributed to this function and to subroutines called from this function. The histogram hits for this function are counted again for the callers of this function. Therefore, adding up these percentages is meaningless. `self' This is the total number of histogram hits for this function. This should be identical to the number printed in the `self' field for this function in the flat profile. `children' This is the total number of histogram hits for subroutine calls made by this function. This should be equal to the sum of all the `self' and `children' entries of the children listed directly below this function. `called' This is the number of times the function was called. If the function called itself recursively, there are two numbers, separated by a `+'. The first number counts non-recursive calls, and the second counts recursive calls. In the example above, the function `report' was called once from `main'. `name' This is the name of the current function. The index number is repeated after it. If the function is part of a cycle of recursion, the cycle number is printed between the function's name and the index number (*note How Mutually Recursive Functions Are Described: Cycles.). For example, if function `gnurr' is part of cycle number one, and has index number twelve, its primary line would be end like this: gnurr [12]  File: gprof.info, Node: Callers, Next: Subroutines, Prev: Primary, Up: Call Graph 5.2.2 Lines for a Function's Callers ------------------------------------ A function's entry has a line for each function it was called by. These lines' fields correspond to the fields of the primary line, but their meanings are different because of the difference in context. For reference, we repeat two lines from the entry for the function `report', the primary line and one caller-line preceding it, together with the heading line that shows the names of the fields: index % self children called name ... 0.00 98.30 1/1 main [2] [3] 100.0 0.00 98.30 1 report [3] Here are the meanings of the fields in the caller-line for `report' called from `main': `self' An estimate of the number of histogram hits for `report' itself when it was called from `main'. `children' An estimate of the number of histogram hits for subroutines of `report' when `report' was called from `main'. The sum of the `self' and `children' fields is an estimate of the number of histogram hits within calls to `report' from `main'. `called' Two numbers: the number of times `report' was called from `main', followed by the total number of non-recursive calls to `report' from all its callers. `name and index number' The name of the caller of `report' to which this line applies, followed by the caller's index number. Not all functions have entries in the call graph; some options to `gprof' request the omission of certain functions. When a caller has no entry of its own, it still has caller-lines in the entries of the functions it calls. If the caller is part of a recursion cycle, the cycle number is printed between the name and the index number. If the identity of the callers of a function cannot be determined, a dummy caller-line is printed which has `' as the "caller's name" and all other fields blank. This can happen for signal handlers.  File: gprof.info, Node: Subroutines, Next: Cycles, Prev: Callers, Up: Call Graph 5.2.3 Lines for a Function's Subroutines ---------------------------------------- A function's entry has a line for each of its subroutines--in other words, a line for each other function that it called. These lines' fields correspond to the fields of the primary line, but their meanings are different because of the difference in context. For reference, we repeat two lines from the entry for the function `main', the primary line and a line for a subroutine, together with the heading line that shows the names of the fields: index % self children called name ... [2] 100.0 0.00 98.30 1 main [2] 0.00 98.30 1/1 report [3] Here are the meanings of the fields in the subroutine-line for `main' calling `report': `self' An estimate of the number of histogram hits directly within `report' when `report' was called from `main'. `children' An estimate of the number of histogram hits in subroutines of `report' when `report' was called from `main'. The sum of the `self' and `children' fields is an estimate of the total histogram hits in calls to `report' from `main'. `called' Two numbers, the number of calls to `report' from `main' followed by the total number of non-recursive calls to `report'. This ratio is used to determine how much of `report''s `self' and `children' time gets credited to `main'. *Note Estimating `children' Times: Assumptions. `name' The name of the subroutine of `main' to which this line applies, followed by the subroutine's index number. If the caller is part of a recursion cycle, the cycle number is printed between the name and the index number.  File: gprof.info, Node: Cycles, Prev: Subroutines, Up: Call Graph 5.2.4 How Mutually Recursive Functions Are Described ---------------------------------------------------- The graph may be complicated by the presence of "cycles of recursion" in the call graph. A cycle exists if a function calls another function that (directly or indirectly) calls (or appears to call) the original function. For example: if `a' calls `b', and `b' calls `a', then `a' and `b' form a cycle. Whenever there are call paths both ways between a pair of functions, they belong to the same cycle. If `a' and `b' call each other and `b' and `c' call each other, all three make one cycle. Note that even if `b' only calls `a' if it was not called from `a', `gprof' cannot determine this, so `a' and `b' are still considered a cycle. The cycles are numbered with consecutive integers. When a function belongs to a cycle, each time the function name appears in the call graph it is followed by `'. The reason cycles matter is that they make the time values in the call graph paradoxical. The "time spent in children" of `a' should include the time spent in its subroutine `b' and in `b''s subroutines--but one of `b''s subroutines is `a'! How much of `a''s time should be included in the children of `a', when `a' is indirectly recursive? The way `gprof' resolves this paradox is by creating a single entry for the cycle as a whole. The primary line of this entry describes the total time spent directly in the functions of the cycle. The "subroutines" of the cycle are the individual functions of the cycle, and all other functions that were called directly by them. The "callers" of the cycle are the functions, outside the cycle, that called functions in the cycle. Here is an example portion of a call graph which shows a cycle containing functions `a' and `b'. The cycle was entered by a call to `a' from `main'; both `a' and `b' called `c'. index % self children called name ---------------------------------------- 1.77 0.00 1/1 main [2] [3] 91.7 1.77 0.00 1+5 [3] 1.02 0.00 3 b [4] 0.75 0.00 2 a [5] ---------------------------------------- 3 a [5] [4] 52.8 1.02 0.00 0 b [4] 2 a [5] 0.00 0.00 3/6 c [6] ---------------------------------------- 1.77 0.00 1/1 main [2] 2 b [4] [5] 38.9 0.75 0.00 1 a [5] 3 b [4] 0 0.00 3/6 c [6] ---------------------------------------- (The entire call graph for this program contains in addition an entry for `main', which calls `a', and an entry for `c', with callers `a' and `b'.) index % self children called name [1] 100.0 0.00 1.93 0 start [1] 0.16 1.77 1/1 main [2] ---------------------------------------- 0.16 1.77 1/1 start [1] [2] 100.0 0.16 1.77 1 main [2] 1.77 0.00 1/1 a [5] ---------------------------------------- 1.77 0.00 1/1 main [2] [3] 91.7 1.77 0.00 1+5 [3] 1.02 0.00 3 b [4] 0.75 0.00 2 a [5] 0.00 0.00 6/6 c [6] ---------------------------------------- 3 a [5] [4] 52.8 1.02 0.00 0 b [4] 2 a [5] 0.00 0.00 3/6 c [6] ---------------------------------------- 1.77 0.00 1/1 main [2] 2 b [4] [5] 38.9 0.75 0.00 1 a [5] 3 b [4] 0.00 0.00 3/6 c [6] ---------------------------------------- 0.00 0.00 3/6 b [4] 0.00 0.00 3/6 a [5] [6] 0.0 0.00 0.00 6 c [6] ---------------------------------------- The `self' field of the cycle's primary line is the total histogram count for all the functions of the cycle. It equals the sum of the `self' fields for the individual functions in the cycle, found in the entry in the subroutine lines for these functions. The `children' fields of the cycle's primary line and subroutine lines count only subroutines outside the cycle. Even though `a' calls `b', the time spent in those calls to `b' is not counted in `a''s `children' time. Thus, we do not encounter the problem of what to do when the time in those calls to `b' includes indirect recursive calls back to `a'. The `children' field of a caller-line in the cycle's entry estimates the number of histogram hits _in the whole cycle_, and its other subroutines, on the times when that caller called a function in the cycle. The `called' field in the primary line for the cycle has two numbers: first, the number of times functions in the cycle were called by functions outside the cycle; second, the number of times they were called by functions in the cycle (including times when a function in the cycle calls itself). This is a generalization of the usual split into non-recursive and recursive calls. The `called' field of a subroutine-line for a cycle member in the cycle's entry says how many time that function was called from functions in the cycle. The total of all these is the second number in the primary line's `called' field. In the individual entry for a function in a cycle, the other functions in the same cycle can appear as subroutines and as callers. These lines show how many times each function in the cycle called or was called from each other function in the cycle. The `self' and `children' fields in these lines are blank because of the difficulty of defining meanings for them when recursion is going on.  File: gprof.info, Node: Line-by-line, Next: Annotated Source, Prev: Call Graph, Up: Output 5.3 Line-by-line Profiling ========================== `gprof''s `-l' option causes the program to perform "line-by-line" profiling. In this mode, histogram samples are assigned not to functions, but to individual lines of source code. The program must be compiled with a `-g' option to generate debugging symbols for tracking source code lines. The flat profile is the most useful output table in line-by-line mode. The call graph isn't as useful as normal, since the current version of `gprof' does not propagate call graph arcs from source code lines to the enclosing function. The call graph does, however, show each line of code that called each function, along with a count. The `-f' option also enables line-by-line profiling. The only difference between `-f' and `-l' is the order of the entries in the flat profile. With `-f', the flat profile entries are grouped by function so that all the lines for a function appear together. The functions are shown in decreasing order of histogram counts, and the lines within each function are also sorted in decreasing order of histogram counts. Here is a section of `gprof''s output, without line-by-line profiling. Note that `ct_init' accounted for 13327 calls to `init_block'. Flat profile: self total cumulative self cycles cycles % cycles cycles calls /call /call name (K) (K) (K) (K) 30.77 0.13 0.04 6335 6.31 6.31 ct_init Call graph (explanation follows) index % self children called name (K) (K) 0.00 0.00 1/13496 name_too_long 0.00 0.00 40/13496 deflate 0.00 0.00 128/13496 deflate_fast 0.00 0.00 13327/13496 ct_init [7] 0.0 0.00 0.00 13496 init_block Now let's look at some of `gprof''s output from the same program run, this time with line-by-line profiling enabled. Note that `ct_init''s histogram hits are broken down into four lines of source code--lines 349, 351, 382 and 385. In the call graph, note how `ct_init''s 13327 calls to `init_block' are broken down into one call from line 396, 3071 calls from line 384, 3730 calls from line 385, and 6525 calls from 387. Flat profile: cumulative self % cycles cycles calls name (K) (K) 7.69 0.10 0.01 ct_init (trees.c:349) 7.69 0.11 0.01 ct_init (trees.c:351) 7.69 0.12 0.01 ct_init (trees.c:382) 7.69 0.13 0.01 ct_init (trees.c:385) Call graph (explanation follows) index % self children called name (K) (K) 0.00 0.00 1/13496 name_too_long (gzip.c:1440) 0.00 0.00 1/13496 deflate (deflate.c:763) 0.00 0.00 1/13496 ct_init (trees.c:396) 0.00 0.00 2/13496 deflate (deflate.c:727) 0.00 0.00 4/13496 deflate (deflate.c:686) 0.00 0.00 5/13496 deflate (deflate.c:675) 0.00 0.00 12/13496 deflate (deflate.c:679) 0.00 0.00 16/13496 deflate (deflate.c:730) 0.00 0.00 128/13496 deflate_fast (deflate.c:654) 0.00 0.00 3071/13496 ct_init (trees.c:384) 0.00 0.00 3730/13496 ct_init (trees.c:385) 0.00 0.00 6525/13496 ct_init (trees.c:387) [6] 0.0 0.00 0.00 13496 init_block (trees.c:408)  File: gprof.info, Node: Annotated Source, Next: Other Events, Prev: Line-by-line, Up: Output 5.4 The Annotated Source Listing ================================ `gprof''s `-A' option triggers an annotated source listing, which lists the program's source code, each function labeled with the number of times it was called. You may also need to specify the `-I' option, if `gprof' can't find the source code files. If you use the Xtensa ISS to profile instruction counts, `gprof' can determine how many times each basic-block of code was executed, and the basic-block execution counts can be seen in the annotated source listing. Run ISS with `--client_cmds="profile --instructions"' to profile instruction counts. If you profile cycle counts (the default), the basic-block execution counts are not available. For example, consider the following function, taken from gzip, with line numbers added: 1 ulg updcrc(s, n) 2 uch *s; 3 unsigned n; 4 { 5 register ulg c; 6 7 static ulg crc = (ulg)0xffffffffL; 8 9 if (s == NULL) { 10 c = 0xffffffffL; 11 } else { 12 c = crc; 13 if (n) do { 14 c = crc_32_tab[...]; 15 } while (--n); 16 } 17 crc = c; 18 return c ^ 0xffffffffL; 19 } `updcrc' has at least five basic-blocks. One is the function itself. The `if' statement on line 9 generates two more basic-blocks, one for each branch of the `if'. A fourth basic-block results from the `if' on line 13, and the contents of the `do' loop form the fifth basic-block. The compiler may also generate additional basic-blocks to handle various special cases. Run `xt-gprof -l -A' for line-by-line annotated source output. The `-x' option is also helpful, to ensure that each line of code is labeled at least once. Here is `updcrc''s annotated source listing for a sample `gzip' run: ulg updcrc(s, n) uch *s; unsigned n; 2 ->{ register ulg c; static ulg crc = (ulg)0xffffffffL; 2 -> if (s == NULL) { 1 -> c = 0xffffffffL; 1 -> } else { 1 -> c = crc; 1 -> if (n) do { 26312 -> c = crc_32_tab[...]; 26312,1,26311 -> } while (--n); } 2 -> crc = c; 2 -> return c ^ 0xffffffffL; 2 ->} In this example, the function was called twice, passing once through each branch of the `if' statement. The body of the `do' loop was executed a total of 26312 times. Note how the `while' statement is annotated. It began execution 26312 times, once for each iteration through the loop. One of those times (the last time) it exited, while it branched back to the beginning of the loop 26311 times.  File: gprof.info, Node: Other Events, Prev: Annotated Source, Up: Output 5.5 Profiling Other Events ========================== When analyzing a program's behavior, it may be helpful to profile events other than cycle counts. The profiling client in the Xtensa ISS can also collect information on events such as cache misses, pipeline interlocks, etc. *Note Executing the Program: Executing. All the features of `gprof' can be used to analyze the profile data, regardless of the kind of events being profiled. The only change is that the histogram counts in the profile data file represent the occurrence of these other events for each instruction. For example, here is an excerpt of the flat profile output when the ISS was used to profile instruction cache misses in a small program: Flat profile: self total cumulative self icmisses icmisses % icmisses icmisses calls /call /call name 28.12 591.00 591.00 296 2.00 2.00 memcpy 12.32 850.00 259.00 86 3.01 3.01 check_range 7.66 1011.00 161.00 117 1.38 1.39 call 6.37 1145.00 134.00 133 1.01 6.60 exec 5.47 1260.00 115.00 38 3.03 3.25 _write_r 5.14 1368.00 108.00 38 2.84 2.84 memchr  File: gprof.info, Node: Inaccuracy, Next: GNU Free Documentation License, Prev: Output, Up: Top 6 Inaccuracy of `gprof' Output ****************************** * Menu: * Sampling Error:: Statistical margins of error * Assumptions:: Estimating children times  File: gprof.info, Node: Sampling Error, Next: Assumptions, Up: Inaccuracy 6.1 Statistical Sampling Error ============================== This section does not apply when profiling with the Xtensa ISS. The ISS collects profile data continuously--there is no sampling involved. For hardware profiling, you can control the sampling errors to some extent by adjusting the sampling frequency with the `xt_profile_set_frequency' function. See the `Xtensa Software Development Toolkit User's Guide' for more information on hardware profiling. The run-time figures that `gprof' gives you are based on a sampling process, so they are subject to statistical inaccuracy. If a function runs only a small amount of time, so that on the average the sampling process ought to catch that function in the act only once, there is a pretty good chance it will actually find that function zero times, or twice. By contrast, the number-of-calls and basic-block figures are derived by counting, not sampling. They are completely accurate and will not vary from run to run if your program is deterministic and single threaded. In multi-threaded applications, or single threaded applications that link with multi-threaded libraries, the counts are only deterministic if the counting function is thread-safe. (Note: beware that the mcount counting function in glibc is _not_ thread-safe). The "sampling period" that is printed at the beginning of the flat profile says how often samples are taken. The rule of thumb is that a run-time figure is accurate if it is considerably bigger than the sampling period. The actual amount of error can be predicted. For N samples, the _expected_ error is the square-root of N. For example, if the sampling period is 0.01 seconds and `foo''s run-time is 1 second, N is 100 samples (1 second/0.01 seconds), sqrt(N) is 10 samples, so the expected error in `foo''s run-time is 0.1 seconds (10*0.01 seconds), or ten percent of the observed value. Again, if the sampling period is 0.01 seconds and `bar''s run-time is 100 seconds, N is 10000 samples, sqrt(N) is 100 samples, so the expected error in `bar''s run-time is 1 second, or one percent of the observed value. It is likely to vary this much _on the average_ from one profiling run to the next. (_Sometimes_ it will vary more.) This does not mean that a small run-time figure is devoid of information. If the program's _total_ run-time is large, a small run-time for one function does tell you that that function used an insignificant fraction of the whole program's time. Usually this means it is not worth optimizing. One way to get more accuracy is to give your program more (but similar) input data so it will take longer. Another way is to combine the data from several runs, using the `-s' option of `gprof'. Here is how: 1. Run your program once. 2. Issue the command `mv gmon.out gmon.sum'. 3. Run your program again, the same as before. 4. Merge the new data in `gmon.out' into `gmon.sum' with this command: xt-gprof -s EXECUTABLE-FILE gmon.out gmon.sum 5. Repeat the last two steps as often as you wish. 6. Analyze the cumulative data using this command: xtgprof EXECUTABLE-FILE gmon.sum > OUTPUT-FILE  File: gprof.info, Node: Assumptions, Prev: Sampling Error, Up: Inaccuracy 6.2 Estimating `children' Times =============================== Some of the figures in the call graph are estimates--for example, the `children' time values and all the time figures in caller and subroutine lines. There is no direct information about these measurements in the profile data itself. Instead, `gprof' estimates them by making an assumption about your program that might or might not be true. The assumption made is that the average time spent in each call to any function `foo' is not correlated with who called `foo'. If `foo' used 5 seconds in all, and 2/5 of the calls to `foo' came from `a', then `foo' contributes 2 seconds to `a''s `children' time, by assumption. This assumption is usually true enough, but for some programs it is far from true. Suppose that `foo' returns very quickly when its argument is zero; suppose that `a' always passes zero as an argument, while other callers of `foo' pass other arguments. In this program, all the time spent in `foo' is in the calls from callers other than `a'. But `gprof' has no way of knowing this; it will blindly and incorrectly charge 2 seconds of time in `foo' to the children of `a'.  File: gprof.info, Node: GNU Free Documentation License, Next: History, Prev: Inaccuracy, Up: Top Appendix A GNU Free Documentation License ***************************************** Version 1.3, 3 November 2008 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. `http://fsf.org/' Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 0. PREAMBLE The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others. This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software. We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference. 1. APPLICABILITY AND DEFINITIONS This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law. A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language. A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) 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COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects. You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document. 7. AGGREGATION WITH INDEPENDENT WORKS A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document. If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate. 8. TRANSLATION Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail. If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title. 9. TERMINATION You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License. However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation. Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice. Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it. 10. FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See `http://www.gnu.org/copyleft/'. Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document. 11. RELICENSING "Massive Multiauthor Collaboration Site" (or "MMC Site") means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A "Massive Multiauthor Collaboration" (or "MMC") contained in the site means any set of copyrightable works thus published on the MMC site. "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization. "Incorporate" means to publish or republish a Document, in whole or in part, as part of another Document. An MMC is "eligible for relicensing" if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008. The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing. ADDENDUM: How to use this License for your documents ==================================================== To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: Copyright (C) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''. If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.  File: gprof.info, Node: History, Prev: GNU Free Documentation License, Up: Top Appendix B History ****************** The original version of this document, entitled "GNU gprof, the GNU Profiler", was written by Jay Fenlason and Richard Stallman. The version for `gprof' 2.18 was released in 2007 and published by the Free Software Foundation. Tensilica, Inc. changed the title to "GNU Profiler User's Guide" and modified the document to include features specific to Xtensa processors. The revised document was published by Tensilica, Inc. on the date shown in the inside cover page. The TeXinfo source files for this modified document are available from `http://www.tensilica.com/gnudocs'.  Tag Table: Node: Top1998 Node: Revisions3144 Node: Introduction3440 Node: Compiling8542 Node: Executing11630 Node: Xtensa ISS12414 Node: Xtensa Hardware15019 Node: Invoking15808 Node: Output Options17093 Node: Analysis Options24281 Node: Miscellaneous Options29200 Node: Symspecs30403 Node: Output32232 Node: Flat Profile33339 Node: Call Graph38541 Node: Primary42141 Node: Callers44735 Node: Subroutines46868 Node: Cycles48723 Node: Line-by-line55660 Node: Annotated Source59795 Node: Other Events62848 Node: Inaccuracy64285 Node: Sampling Error64564 Node: Assumptions67823 Node: GNU Free Documentation License69078 Node: History94243  End Tag Table