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134 lines
5.8 KiB
HTML
134 lines
5.8 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the gprof profiler of the GNU system.
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Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License".
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-->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Introduction (GNU gprof)</title>
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<meta name="description" content="Introduction (GNU gprof)">
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<meta name="keywords" content="Introduction (GNU gprof)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="index.html#Top" rel="up" title="Top">
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<link href="Compiling.html#Compiling" rel="next" title="Compiling">
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<link href="index.html#Top" rel="prev" title="Top">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Introduction"></a>
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<div class="header">
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<p>
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Next: <a href="Compiling.html#Compiling" accesskey="n" rel="next">Compiling</a>, Previous: <a href="index.html#Top" accesskey="p" rel="prev">Top</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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</div>
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<hr>
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<a name="Introduction-to-Profiling"></a>
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<h2 class="chapter">1 Introduction to Profiling</h2>
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<p>Profiling allows you to learn where your program spent its time and which
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functions called which other functions while it was executing. This
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information can show you which pieces of your program are slower than you
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expected, and might be candidates for rewriting to make your program
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execute faster. It can also tell you which functions are being called more
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or less often than you expected. This may help you spot bugs that had
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otherwise been unnoticed.
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</p>
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<p>Since the profiler uses information collected during the actual execution
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of your program, it can be used on programs that are too large or too
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complex to analyze by reading the source. However, how your program is run
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will affect the information that shows up in the profile data. If you
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don’t use some feature of your program while it is being profiled, no
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profile information will be generated for that feature.
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</p>
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<p>Profiling has several steps:
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</p>
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<ul>
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<li> You must compile and link your program with profiling enabled.
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See <a href="Compiling.html#Compiling">Compiling a Program for Profiling</a>.
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</li><li> You must execute your program to generate a profile data file.
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See <a href="Executing.html#Executing">Executing the Program</a>.
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</li><li> You must run <code>gprof</code> to analyze the profile data.
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See <a href="Invoking.html#Invoking"><code>gprof</code> Command Summary</a>.
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</li></ul>
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<p>The next three chapters explain these steps in greater detail.
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</p>
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<p>Several forms of output are available from the analysis.
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</p>
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<p>The <em>flat profile</em> shows how much time your program spent in each function,
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and how many times that function was called. If you simply want to know
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which functions burn most of the cycles, it is stated concisely here.
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See <a href="Flat-Profile.html#Flat-Profile">The Flat Profile</a>.
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</p>
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<p>The <em>call graph</em> shows, for each function, which functions called it, which
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other functions it called, and how many times. There is also an estimate
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of how much time was spent in the subroutines of each function. This can
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suggest places where you might try to eliminate function calls that use a
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lot of time. See <a href="Call-Graph.html#Call-Graph">The Call Graph</a>.
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</p>
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<p>The <em>annotated source</em> listing is a copy of the program’s
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source code, labeled with the number of times each line of the
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program was executed. See <a href="Annotated-Source.html#Annotated-Source">The Annotated Source
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Listing</a>.
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</p>
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<p>To better understand how profiling works, you may wish to read
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a description of its implementation.
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See <a href="Implementation.html#Implementation">Implementation of Profiling</a>.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Compiling.html#Compiling" accesskey="n" rel="next">Compiling</a>, Previous: <a href="index.html#Top" accesskey="p" rel="prev">Top</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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</div>
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</body>
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</html>
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