<html lang="en"> <head> <title>How do I? - GNU gprof</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="GNU gprof"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="prev" href="Inaccuracy.html#Inaccuracy" title="Inaccuracy"> <link rel="next" href="Incompatibilities.html#Incompatibilities" title="Incompatibilities"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- This file documents the gprof profiler of the GNU system. Copyright (C) 1988-2015 Free Software Foundation, 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''. --> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="How-do-I%3f"></a> <a name="How-do-I_003f"></a> <p> Next: <a rel="next" accesskey="n" href="Incompatibilities.html#Incompatibilities">Incompatibilities</a>, Previous: <a rel="previous" accesskey="p" href="Inaccuracy.html#Inaccuracy">Inaccuracy</a>, Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a> <hr> </div> <h2 class="chapter">7 Answers to Common Questions</h2> <dl> <dt>How can I get more exact information about hot spots in my program?<dd> Looking at the per-line call counts only tells part of the story. Because <code>gprof</code> can only report call times and counts by function, the best way to get finer-grained information on where the program is spending its time is to re-factor large functions into sequences of calls to smaller ones. Beware however that this can introduce artificial hot spots since compiling with ‘<samp><span class="samp">-pg</span></samp>’ adds a significant overhead to function calls. An alternative solution is to use a non-intrusive profiler, e.g. oprofile. <br><dt>How do I find which lines in my program were executed the most times?<dd> Use the <code>gcov</code> program. <br><dt>How do I find which lines in my program called a particular function?<dd> Use ‘<samp><span class="samp">gprof -l</span></samp>’ and lookup the function in the call graph. The callers will be broken down by function and line number. <br><dt>How do I analyze a program that runs for less than a second?<dd> Try using a shell script like this one: <pre class="example"> for i in `seq 1 100`; do fastprog mv gmon.out gmon.out.$i done gprof -s fastprog gmon.out.* gprof fastprog gmon.sum </pre> <p>If your program is completely deterministic, all the call counts will be simple multiples of 100 (i.e., a function called once in each run will appear with a call count of 100). </dl> </body></html>