doc/guide/localhost/ProfilingAllocation

   1 <!DOCTYPE html>
   2 <html lang="en">
   3 <head>
   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">
   9
  10
  11 <script type="text/javascript" src="./asciidoc.js"></script>
  12 <script type="text/javascript">
  13 /*<![CDATA[*/
  14 asciidoc.install();
  15 /*]]>*/
  16 </script>
  17 <link rel="stylesheet" href="./mlton.css" type="text/css">
  18 </head>
  19 <body class="article">
  20 <div id="banner">
  21 <div id="banner-home">
  22 <a href="./Home">MLton 20180207</a>
  23 </div>
  24 </div>
  25 <div id="header">
  26 <h1>ProfilingAllocation</h1>
  27 </div>
  28 <div id="content">
  29 <div id="preamble">
  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">=&gt;</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">=&gt;</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>
  40
  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">=&gt;</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">=&gt;</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>
  45
  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">=&gt;</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
  53 % ./list-rev
  54 % mlprof -show-line true list-rev mlmon.out
  55 6,030,136 bytes allocated (108,336 bytes by GC)
  56        function          cur
  57 ----------------------- -----
  58 append  list-rev.sml: 1 97.6%
  59 &lt;gc&gt;                     1.8%
  60 &lt;main&gt;                   0.4%
  61 rev  list-rev.sml: 6     0.2%</pre>
  62 </div></div>
  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>
  74 </div>
  75 </div>
  76 </div>
  77 <div id="footnotes"><hr></div>
  78 <div id="footer">
  79 <div id="footer-text">
  80 </div>
  81 <div id="footer-badges">
  82 </div>
  83 </div>
  84 </body>
  85 </html>