439 lines
17 KiB
Plaintext
439 lines
17 KiB
Plaintext
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Sun Feb 5 16:09:16 1995
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This file documents the changes and new features available with this
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version of GNU gprof.
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* New Features
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o Long options
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o Supports generalized file format, without breaking backward compatibility:
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new file format supports basic-block execution counts and non-realtime
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histograms (see below)
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o Supports profiling at the line level: flat profiles, call-graph profiles,
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and execution-counts can all be displayed at a level that identifies
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individual lines rather than just functions
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o Test-coverage support (similar to Sun tcov program): source files
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can be annotated with the number of times a function was invoked
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or with the number of times each basic-block in a function was
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executed
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o Generalized histograms: not just execution-time, but arbitrary
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histograms are support (for example, performance counter based
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profiles)
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o Powerful mechanism to select data to be included/excluded from
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analysis and/or output
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o Support for DEC OSF/1 v3.0
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o Full cross-platform profiling support: gprof uses BFD to support
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arbitrary, non-native object file formats and non-native byte-orders
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(this feature has not been tested yet)
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o In the call-graph function index, static function names are now
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printed together with the filename in which the function was defined
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(required bfd_find_nearest_line() support and symbolic debugging
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information to be present in the executable file)
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o Major overhaul of source code (compiles cleanly with -Wall, etc.)
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* Supported Platforms
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The current version is known to work on:
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o DEC OSF/1 v3.0
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All features supported.
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o SunOS 4.1.x
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All features supported.
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o Solaris 2.3
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Line-level profiling unsupported because bfd_find_nearest_line()
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is not fully implemented for Elf binaries.
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o HP-UX 9.01
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Line-level profiling unsupported because bfd_find_nearest_line()
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is not fully implemented for SOM binaries.
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* Detailed Description
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** User Interface Changes
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The command-line interface is backwards compatible with earlier
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versions of GNU gprof and Berkeley gprof. The only exception is
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the option to delete arcs from the call graph. The old syntax
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was:
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-k fromname toname
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while the new syntax is:
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-k fromname/toname
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This change was necessary to be compatible with long-option parsing.
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Also, "fromname" and "toname" can now be arbitrary symspecs rather
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than just function names (see below for an explanation of symspecs).
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For example, option "-k gprof.c/" suppresses all arcs due to calls out
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of file "gprof.c".
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*** Sym Specs
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It is often necessary to apply gprof only to specific parts of a
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program. GNU gprof has a simple but powerful mechanism to achieve
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this. So called {\em symspecs\/} provide the foundation for this
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mechanism. A symspec selects the parts of a profiled program to which
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an operation should be applied to. The syntax of a symspec is
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simple:
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filename_containing_a_dot
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| funcname_not_containing_a_dot
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| linenumber
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| ( [ any_filename ] `:' ( any_funcname | linenumber ) )
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Here are some examples:
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main.c Selects everything in file "main.c"---the
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dot in the string tells gprof to interpret
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the string as a filename, rather than as
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a function name. To select a file whose
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name does contain a dot, a trailing colon
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should be specified. For example, "odd:" is
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interpreted as the file named "odd".
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main Selects all functions named "main". Notice
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that there may be multiple instances of the
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same function name because some of the
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definitions may be local (i.e., static).
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Unless a function name is unique in a program,
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you must use the colon notation explained
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below to specify a function from a specific
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source file. Sometimes, functionnames contain
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dots. In such cases, it is necessar to
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add a leading colon to the name. For example,
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":.mul" selects function ".mul".
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main.c:main Selects function "main" in file "main.c".
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main.c:134 Selects line 134 in file "main.c".
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IMPLEMENTATION NOTE: The source code uses the type sym_id for symspecs.
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At some point, this probably ought to be changed to "sym_spec" to make
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reading the code easier.
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*** Long options
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GNU gprof now supports long options. The following is a list of all
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supported options. Options that are listed without description
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operate in the same manner as the corresponding option in older
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versions of gprof.
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Short Form: Long Form:
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----------- ----------
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-l --line
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Request profiling at the line-level rather
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than just at the function level. Source
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lines are identified by symbols of the form:
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func (file:line)
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where "func" is the function name, "file" is the
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file name and "line" is the line-number that
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corresponds to the line.
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To work properly, the binary must contain symbolic
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debugging information. This means that the source
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have to be translated with option "-g" specified.
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Functions for which there is no symbolic debugging
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information available are treated as if "--line"
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had not been specified. However, the line number
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printed with such symbols is usually incorrect
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and should be ignored.
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-a --no-static
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-A[symspec] --annotated-source[=symspec]
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Request output in the form of annotated source
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files. If "symspec" is specified, print output only
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for symbols selected by "symspec". If the option
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is specified multiple times, annotated output is
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generated for the union of all symspecs.
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Examples:
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-A Prints annotated source for all
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source files.
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-Agprof.c Prints annotated source for file
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gprof.c.
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-Afoobar Prints annotated source for files
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containing a function named "foobar".
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The entire file will be printed, but
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only the function itself will be
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annotated with profile data.
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-J[symspec] --no-annotated-source[=symspec]
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Suppress annotated source output. If specified
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without argument, annotated output is suppressed
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completely. With an argument, annotated output
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is suppressed only for the symbols selected by
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"symspec". If the option is specified multiple
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times, annotated output is suppressed for the
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union of all symspecs. This option has lower
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precedence than --annotated-source
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-p[symspec] --flat-profile[=symspec]
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Request output in the form of a flat profile
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(unless any other output-style option is specified,
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this option is turned on by default). If
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"symspec" is specified, include only symbols
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selected by "symspec" in flat profile. If the
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option is specified multiple times, the flat
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profile includes symbols selected by the union
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of all symspecs.
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-P[symspec] --no-flat-profile[=symspec]
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Suppress output in the flat profile. If given
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without an argument, the flat profile is suppressed
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completely. If "symspec" is specified, suppress
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the selected symbols in the flat profile. If the
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option is specified multiple times, the union of
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the selected symbols is suppressed. This option
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has lower precedence than --flat-profile.
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-q[symspec] --graph[=symspec]
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Request output in the form of a call-graph
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(unless any other output-style option is specified,
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this option is turned on by default). If "symspec"
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is specified, include only symbols selected by
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"symspec" in the call-graph. If the option is
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specified multiple times, the call-graph includes
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symbols selected by the union of all symspecs.
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-Q[symspec] --no-graph[=symspec]
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Suppress output in the call-graph. If given without
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an argument, the call-graph is suppressed completely.
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With a "symspec", suppress the selected symbols
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from the call-graph. If the option is specified
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multiple times, the union of the selected symbols
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is suppressed. This option has lower precedence
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than --graph.
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-C[symspec] --exec-counts[=symspec]
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Request output in the form of execution counts.
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If "symspec" is present, include only symbols
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selected by "symspec" in the execution count
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listing. If the option is specified multiple
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times, the execution count listing includes
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symbols selected by the union of all symspecs.
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-Z[symspec] --no-exec-counts[=symspec]
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Suppress output in the execution count listing.
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If given without an argument, the listing is
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suppressed completely. With a "symspec", suppress
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the selected symbols from the call-graph. If the
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option is specified multiple times, the union of
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the selected symbols is suppressed. This option
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has lower precedence than --exec-counts.
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-i --file-info
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Print information about the profile files that
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are read. The information consists of the
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number and types of records present in the
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profile file. Currently, a profile file can
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contain any number and any combination of histogram,
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call-graph, or basic-block count records.
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-s --sum
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-x --all-lines
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This option affects annotated source output only.
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By default, only the lines at the beginning of
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a basic-block are annotated. If this option is
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specified, every line in a basic-block is annotated
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by repeating the annotation for the first line.
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This option is identical to tcov's "-a".
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-I dirs --directory-path=dirs
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This option affects annotated source output only.
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Specifies the list of directories to be searched
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for source files. The argument "dirs" is a colon
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separated list of directories. By default, gprof
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searches for source files relative to the current
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working directory only.
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-z --display-unused-functions
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-m num --min-count=num
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This option affects annotated source and execution
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count output only. Symbols that are executed
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less than "num" times are suppressed. For annotated
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source output, suppressed symbols are marked
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by five hash-marks (#####). In an execution count
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output, suppressed symbols do not appear at all.
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-L --print-path
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Normally, source filenames are printed with the path
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component suppressed. With this option, gprof
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can be forced to print the full pathname of
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source filenames. The full pathname is determined
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from symbolic debugging information in the image file
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and is relative to the directory in which the compiler
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was invoked.
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-y --separate-files
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This option affects annotated source output only.
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Normally, gprof prints annotated source files
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to standard-output. If this option is specified,
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annotated source for a file named "path/filename"
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is generated in the file "filename-ann". That is,
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annotated output is {\em always\/} generated in
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gprof's current working directory. Care has to
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be taken if a program consists of files that have
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identical filenames, but distinct paths.
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-c --static-call-graph
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-t num --table-length=num
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This option affects annotated source output only.
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After annotating a source file, gprof generates
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an execution count summary consisting of a table
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of lines with the top execution counts. By
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default, this table is ten entries long.
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This option can be used to change the table length
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or, by specifying an argument value of 0, it can be
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suppressed completely.
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-n symspec --time=symspec
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Only symbols selected by "symspec" are considered
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in total and percentage time computations.
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However, this option does not affect percentage time
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computation for the flat profile.
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If the option is specified multiple times, the union
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of all selected symbols is used in time computations.
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-N --no-time=symspec
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Exclude the symbols selected by "symspec" from
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total and percentage time computations.
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However, this option does not affect percentage time
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computation for the flat profile.
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This option is ignored if any --time options are
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specified.
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-w num --width=num
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Sets the output line width. Currently, this option
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affects the printing of the call-graph function index
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only.
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-e <no long form---for backwards compatibility only>
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-E <no long form---for backwards compatibility only>
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-f <no long form---for backwards compatibility only>
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-F <no long form---for backwards compatibility only>
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-k <no long form---for backwards compatibility only>
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-b --brief
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-dnum --debug[=num]
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-h --help
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Prints a usage message.
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-O name --file-format=name
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Selects the format of the profile data files.
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Recognized formats are "auto", "bsd", "magic",
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and "prof". The last one is not yet supported.
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Format "auto" attempts to detect the file format
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automatically (this is the default behavior).
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It attempts to read the profile data files as
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"magic" files and if this fails, falls back to
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the "bsd" format. "bsd" forces gprof to read
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the data files in the BSD format. "magic" forces
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gprof to read the data files in the "magic" format.
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-T --traditional
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-v --version
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** File Format Changes
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The old BSD-derived format used for profile data does not contain a
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magic cookie that allows to check whether a data file really is a
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gprof file. Furthermore, it does not provide a version number, thus
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rendering changes to the file format almost impossible. GNU gprof
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uses a new file format that provides these features. For backward
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compatibility, GNU gprof continues to support the old BSD-derived
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format, but not all features are supported with it. For example,
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basic-block execution counts cannot be accommodated by the old file
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format.
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The new file format is defined in header file \file{gmon_out.h}. It
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consists of a header containing the magic cookie and a version number,
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as well as some spare bytes available for future extensions. All data
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in a profile data file is in the native format of the host on which
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the profile was collected. GNU gprof adapts automatically to the
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byte-order in use.
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In the new file format, the header is followed by a sequence of
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records. Currently, there are three different record types: histogram
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records, call-graph arc records, and basic-block execution count
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records. Each file can contain any number of each record type. When
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reading a file, GNU gprof will ensure records of the same type are
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||
|
|
compatible with each other and compute the union of all records. For
|
||
|
|
example, for basic-block execution counts, the union is simply the sum
|
||
|
|
of all execution counts for each basic-block.
|
||
|
|
|
||
|
|
*** Histogram Records
|
||
|
|
|
||
|
|
Histogram records consist of a header that is followed by an array of
|
||
|
|
bins. The header contains the text-segment range that the histogram
|
||
|
|
spans, the size of the histogram in bytes (unlike in the old BSD
|
||
|
|
format, this does not include the size of the header), the rate of the
|
||
|
|
profiling clock, and the physical dimension that the bin counts
|
||
|
|
represent after being scaled by the profiling clock rate. The
|
||
|
|
physical dimension is specified in two parts: a long name of up to 15
|
||
|
|
characters and a single character abbreviation. For example, a
|
||
|
|
histogram representing real-time would specify the long name as
|
||
|
|
"seconds" and the abbreviation as "s". This feature is useful for
|
||
|
|
architectures that support performance monitor hardware (which,
|
||
|
|
fortunately, is becoming increasingly common). For example, under DEC
|
||
|
|
OSF/1, the "uprofile" command can be used to produce a histogram of,
|
||
|
|
say, instruction cache misses. In this case, the dimension in the
|
||
|
|
histogram header could be set to "i-cache misses" and the abbreviation
|
||
|
|
could be set to "1" (because it is simply a count, not a physical
|
||
|
|
dimension). Also, the profiling rate would have to be set to 1 in
|
||
|
|
this case.
|
||
|
|
|
||
|
|
Histogram bins are 16-bit numbers and each bin represent an equal
|
||
|
|
amount of text-space. For example, if the text-segment is one
|
||
|
|
thousand bytes long and if there are ten bins in the histogram, each
|
||
|
|
bin represents one hundred bytes.
|
||
|
|
|
||
|
|
|
||
|
|
*** Call-Graph Records
|
||
|
|
|
||
|
|
Call-graph records have a format that is identical to the one used in
|
||
|
|
the BSD-derived file format. It consists of an arc in the call graph
|
||
|
|
and a count indicating the number of times the arc was traversed
|
||
|
|
during program execution. Arcs are specified by a pair of addresses:
|
||
|
|
the first must be within caller's function and the second must be
|
||
|
|
within the callee's function. When performing profiling at the
|
||
|
|
function level, these addresses can point anywhere within the
|
||
|
|
respective function. However, when profiling at the line-level, it is
|
||
|
|
better if the addresses are as close to the call-site/entry-point as
|
||
|
|
possible. This will ensure that the line-level call-graph is able to
|
||
|
|
identify exactly which line of source code performed calls to a
|
||
|
|
function.
|
||
|
|
|
||
|
|
*** Basic-Block Execution Count Records
|
||
|
|
|
||
|
|
Basic-block execution count records consist of a header followed by a
|
||
|
|
sequence of address/count pairs. The header simply specifies the
|
||
|
|
length of the sequence. In an address/count pair, the address
|
||
|
|
identifies a basic-block and the count specifies the number of times
|
||
|
|
that basic-block was executed. Any address within the basic-address can
|
||
|
|
be used.
|
||
|
|
|
||
|
|
IMPLEMENTATION NOTE: gcc -a can be used to instrument a program to
|
||
|
|
record basic-block execution counts. However, the __bb_exit_func()
|
||
|
|
that is currently present in libgcc2.c does not generate a gmon.out
|
||
|
|
file in a suiteable format. This should be fixed for future releases
|
||
|
|
of gcc. In the meantime, contact davidm@cs.arizona.edu for a version
|
||
|
|
of __bb_exit_func() to is appropriate.
|