4 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
5 <meta name="generator" content="AsciiDoc 8.6.9">
6 <title>ProfilingAllocation</title>
7 <link rel="stylesheet" href="./asciidoc.css" type="text/css">
8 <link rel="stylesheet" href="./pygments.css" type="text/css">
11 <script type="text/javascript" src="./asciidoc.js"></script>
12 <script type="text/javascript">
17 <link rel="stylesheet" href="./mlton.css" type="text/css">
19 <body class="article">
21 <div id="banner-home">
22 <a href="./Home">MLton 20180207</a>
26 <h1>ProfilingAllocation</h1>
30 <div class="sectionbody">
31 <div class="paragraph"><p>With MLton and <span class="monospaced">mlprof</span>, you can <a href="Profiling">profile</a> your program to
32 find out how many bytes each function allocates. To do so, compile
33 your program with <span class="monospaced">-profile alloc</span>. For example, suppose that
34 <span class="monospaced">list-rev.sml</span> is the following.</p></div>
35 <div class="listingblock">
36 <div class="content"><div class="highlight"><pre><span class="k">fun</span><span class="w"> </span><span class="n">append</span><span class="w"> </span><span class="p">(</span><span class="n">l1</span><span class="p">,</span><span class="w"> </span><span class="n">l2</span><span class="p">)</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
37 <span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">l1</span><span class="w"> </span><span class="k">of</span><span class="w"></span>
38 <span class="w"> </span><span class="p">[]</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">l2</span><span class="w"></span>
39 <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="n">::</span><span class="w"> </span><span class="n">l1</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="n">::</span><span class="w"> </span><span class="n">append</span><span class="w"> </span><span class="p">(</span><span class="n">l1</span><span class="p">,</span><span class="w"> </span><span class="n">l2</span><span class="p">)</span><span class="w"></span>
41 <span class="k">fun</span><span class="w"> </span><span class="n">rev</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
42 <span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="k">of</span><span class="w"></span>
43 <span class="w"> </span><span class="p">[]</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="p">[]</span><span class="w"></span>
44 <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="n">::</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">append</span><span class="w"> </span><span class="p">(</span><span class="n">rev</span><span class="w"> </span><span class="n">l</span><span class="p">,</span><span class="w"> </span><span class="p">[</span><span class="n">x</span><span class="p">])</span><span class="w"></span>
46 <span class="k">val</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">List</span><span class="p">.</span><span class="n">tabulate</span><span class="w"> </span><span class="p">(</span><span class="mi">1000</span><span class="p">,</span><span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"></span>
47 <span class="k">val</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="n">+</span><span class="w"> </span><span class="n">hd</span><span class="w"> </span><span class="p">(</span><span class="n">rev</span><span class="w"> </span><span class="n">l</span><span class="p">)</span><span class="w"></span>
48 </pre></div></div></div>
49 <div class="paragraph"><p>Compile and run <span class="monospaced">list-rev</span> as follows.</p></div>
50 <div class="listingblock">
51 <div class="content monospaced">
52 <pre>% mlton -profile alloc list-rev.sml
54 % mlprof -show-line true list-rev mlmon.out
55 6,030,136 bytes allocated (108,336 bytes by GC)
57 ----------------------- -----
58 append list-rev.sml: 1 97.6%
61 rev list-rev.sml: 6 0.2%</pre>
63 <div class="paragraph"><p>The data shows that most of the allocation is done by the <span class="monospaced">append</span>
64 function defined on line 1 of <span class="monospaced">list-rev.sml</span>. The table also shows
65 how special functions like <span class="monospaced">gc</span> and <span class="monospaced">main</span> are handled: they are
66 printed with surrounding brackets. C functions are displayed
67 similarly. In this example, the allocation done by the garbage
68 collector is due to stack growth, which is usually the case.</p></div>
69 <div class="paragraph"><p>The run-time performance impact of allocation profiling is noticeable,
70 because it inserts additional C calls for object allocation.</p></div>
71 <div class="paragraph"><p>Compile with <span class="monospaced">-profile alloc -profile-branch true</span> to find out how
72 much allocation is done in each branch of a function; see
73 <a href="ProfilingCounts">ProfilingCounts</a> for more details on <span class="monospaced">-profile-branch</span>.</p></div>
77 <div id="footnotes"><hr></div>
79 <div id="footer-text">
81 <div id="footer-badges">