<html lang="en">
<head>
<title>Line-by-line - 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="up" href="Output.html#Output" title="Output">
<link rel="prev" href="Call-Graph.html#Call-Graph" title="Call Graph">
<link rel="next" href="Annotated-Source.html#Annotated-Source" title="Annotated Source">
<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="Line-by-line"></a>
<a name="Line_002dby_002dline"></a>
<p>
Next: <a rel="next" accesskey="n" href="Annotated-Source.html#Annotated-Source">Annotated Source</a>,
Previous: <a rel="previous" accesskey="p" href="Call-Graph.html#Call-Graph">Call Graph</a>,
Up: <a rel="up" accesskey="u" href="Output.html#Output">Output</a>
<hr>
</div>
<h3 class="section">5.3 Line-by-line Profiling</h3>
<p><code>gprof</code>'s ‘<samp><span class="samp">-l</span></samp>’ option causes the program to perform
<dfn>line-by-line</dfn> profiling. In this mode, histogram
samples are assigned not to functions, but to individual
lines of source code. This only works with programs compiled with
older versions of the <code>gcc</code> compiler. Newer versions of <code>gcc</code>
use a different program - <code>gcov</code> - to display line-by-line
profiling information.
<p>With the older versions of <code>gcc</code> the program usually has to be
compiled with a ‘<samp><span class="samp">-g</span></samp>’ option, in addition to ‘<samp><span class="samp">-pg</span></samp>’, in order
to generate debugging symbols for tracking source code lines.
Note, in much older versions of <code>gcc</code> the program had to be
compiled with the ‘<samp><span class="samp">-a</span></samp>’ command line option as well.
<p>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 <code>gprof</code> 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.
<p>Here is a section of <code>gprof</code>'s output, without line-by-line profiling.
Note that <code>ct_init</code> accounted for four histogram hits, and
13327 calls to <code>init_block</code>.
<pre class="smallexample"> Flat profile:
Each sample counts as 0.01 seconds.
% cumulative self self total
time seconds seconds calls us/call us/call name
30.77 0.13 0.04 6335 6.31 6.31 ct_init
Call graph (explanation follows)
granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
index % time self children called name
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
</pre>
<p>Now let's look at some of <code>gprof</code>'s output from the same program run,
this time with line-by-line profiling enabled. Note that <code>ct_init</code>'s
four histogram hits are broken down into four lines of source code—one hit
occurred on each of lines 349, 351, 382 and 385. In the call graph,
note how
<code>ct_init</code>'s 13327 calls to <code>init_block</code> are broken down
into one call from line 396, 3071 calls from line 384, 3730 calls
from line 385, and 6525 calls from 387.
<pre class="smallexample"> Flat profile:
Each sample counts as 0.01 seconds.
% cumulative self
time seconds seconds calls name
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)
granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
% time self children called name
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)
</pre>
</body></html>