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<a class = mltona href="Home">MLton 20061025</a>
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ProfilingAllocation
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With MLton and <tt>mlprof</tt>, you can <a href="Profiling">profile</a> your program to find out how many bytes each function allocates. To do so, compile your program with <tt>-profile alloc</tt>. For example, suppose that <tt>list-rev.sml</tt> is the following. <p>
<pre class=code><B><FONT COLOR="#A020F0">fun </FONT></B><B><FONT COLOR="#0000FF"><B><I><FONT COLOR="#000000">append</FONT></I></B></FONT></B> (l1, l2) <B><FONT COLOR="#5F9EA0">=</FONT></B>
<B><FONT COLOR="#A020F0">case</FONT></B> l1 <B><FONT COLOR="#A020F0">of</FONT></B>
[] <B><FONT COLOR="#5F9EA0">=</FONT></B><B><FONT COLOR="#5F9EA0">></FONT></B> l2
<B><FONT COLOR="#5F9EA0">|</FONT></B> x <B><FONT COLOR="#5F9EA0">::</FONT></B> l1 <B><FONT COLOR="#5F9EA0">=</FONT></B><B><FONT COLOR="#5F9EA0">></FONT></B> x <B><FONT COLOR="#5F9EA0">::</FONT></B> append (l1, l2)
<B><FONT COLOR="#A020F0">fun </FONT></B><B><FONT COLOR="#0000FF"><B><I><FONT COLOR="#000000">rev</FONT></I></B></FONT></B> l <B><FONT COLOR="#5F9EA0">=</FONT></B>
<B><FONT COLOR="#A020F0">case</FONT></B> l <B><FONT COLOR="#A020F0">of</FONT></B>
[] <B><FONT COLOR="#5F9EA0">=</FONT></B><B><FONT COLOR="#5F9EA0">></FONT></B> []
<B><FONT COLOR="#5F9EA0">|</FONT></B> x <B><FONT COLOR="#5F9EA0">::</FONT></B> l <B><FONT COLOR="#5F9EA0">=</FONT></B><B><FONT COLOR="#5F9EA0">></FONT></B> append (rev l, [x])
<B><FONT COLOR="#A020F0">val</FONT></B> l <B><FONT COLOR="#5F9EA0">=</FONT></B> List.tabulate (1000, <B><FONT COLOR="#A020F0">fn</FONT></B> i <B><FONT COLOR="#5F9EA0">=</FONT></B><B><FONT COLOR="#5F9EA0">></FONT></B> i)
<B><FONT COLOR="#A020F0">val</FONT></B> _ <B><FONT COLOR="#5F9EA0">=</FONT></B> 1 <B><FONT COLOR="#5F9EA0">+</FONT></B> <B><FONT COLOR="#5F9EA0">hd</FONT></B> (rev l)
</PRE>
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<p>
Compile and run <tt>list-rev</tt> as follows.
</p>
<pre>% mlton -profile alloc list-rev.sml
% ./list-rev
% mlprof -show-line true list-rev mlmon.out
6,030,136 bytes allocated (108,336 bytes by GC)
function cur
----------------------- -----
append list-rev.sml: 1 97.6%
<gc> 1.8%
<main> 0.4%
rev list-rev.sml: 6 0.2%
</pre><p>
The data shows that most of the allocation is done by the <tt>append</tt> function defined on line 1 of <tt>list-rev.sml</tt>. The table also shows how special functions like <tt>gc</tt> and <tt>main</tt> are handled: they are printed with surrounding brackets. C functions are displayed similarly. In this example, the allocation done by the garbage collector is due to stack growth, which is usually the case.
</p>
<p>
The run-time performance impact of allocation profiling is noticeable, because it inserts additional C calls for object allocation.
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<p>
Compile with <tt>-profile alloc -profile-branch true</tt> to find out how much allocation is done in each branch of a function; see <a href="ProfilingCounts">ProfilingCounts</a> for more details on <tt>-profile-branch</tt>.
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Last edited on 2005-12-02 04:24:10 by <span title="ppp-71-139-183-221.dsl.snfc21.pacbell.net"><a href="StephenWeeks">StephenWeeks</a></span>.
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