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121 lines
4.4 KiB
HTML
121 lines
4.4 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>How do I? (GNU gprof)</title>
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<meta name="description" content="How do I? (GNU gprof)">
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<meta name="keywords" content="How do I? (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="Incompatibilities.html#Incompatibilities" rel="next" title="Incompatibilities">
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<link href="Assumptions.html#Assumptions" rel="prev" title="Assumptions">
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<style type="text/css">
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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="How-do-I_003f"></a>
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<div class="header">
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<p>
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Next: <a href="Incompatibilities.html#Incompatibilities" accesskey="n" rel="next">Incompatibilities</a>, Previous: <a href="Inaccuracy.html#Inaccuracy" accesskey="p" rel="prev">Inaccuracy</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="Answers-to-Common-Questions"></a>
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<h2 class="chapter">7 Answers to Common Questions</h2>
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<dl compact="compact">
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<dt>How can I get more exact information about hot spots in my program?</dt>
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<dd>
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<p>Looking at the per-line call counts only tells part of the story.
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Because <code>gprof</code> can only report call times and counts by function,
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the best way to get finer-grained information on where the program
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is spending its time is to re-factor large functions into sequences
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of calls to smaller ones. Beware however that this can introduce
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artificial hot spots since compiling with ‘<samp>-pg</samp>’ adds a significant
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overhead to function calls. An alternative solution is to use a
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non-intrusive profiler, e.g. oprofile.
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</p>
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</dd>
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<dt>How do I find which lines in my program were executed the most times?</dt>
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<dd>
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<p>Use the <code>gcov</code> program.
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</p>
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</dd>
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<dt>How do I find which lines in my program called a particular function?</dt>
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<dd>
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<p>Use ‘<samp>gprof -l</samp>’ and lookup the function in the call graph.
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The callers will be broken down by function and line number.
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</p>
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</dd>
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<dt>How do I analyze a program that runs for less than a second?</dt>
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<dd>
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<p>Try using a shell script like this one:
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</p>
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<div class="example">
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<pre class="example">for i in `seq 1 100`; do
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fastprog
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mv gmon.out gmon.out.$i
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done
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gprof -s fastprog gmon.out.*
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gprof fastprog gmon.sum
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</pre></div>
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<p>If your program is completely deterministic, all the call counts
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will be simple multiples of 100 (i.e., a function called once in
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each run will appear with a call count of 100).
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</p>
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</dd>
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</dl>
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</body>
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</html>
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