<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en-us" xml:lang="en-us"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="security" content="public" /> <meta name="Robots" content="index,follow" /> <meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' /> <meta name="DC.Type" content="concept" /> <meta name="DC.Title" content="Just-In-Time compiler" /> <meta name="abstract" content="A Just-In-Time (JIT) compiler is a platform-specific compiler that generates machine instructions for each method as needed." /> <meta name="description" content="A Just-In-Time (JIT) compiler is a platform-specific compiler that generates machine instructions for each method as needed." /> <meta name="DC.Relation" scheme="URI" content="runtperf.htm" /> <meta name="DC.Relation" scheme="URI" content="jitde.htm" /> <meta name="copyright" content="(C) Copyright IBM Corporation 2006" /> <meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" /> <meta name="DC.Format" content="XHTML" /> <meta name="DC.Identifier" content="jit" /> <meta name="DC.Language" content="en-us" /> <!-- All rights reserved. Licensed Materials Property of IBM --> <!-- US Government Users Restricted Rights --> <!-- Use, duplication or disclosure restricted by --> <!-- GSA ADP Schedule Contract with IBM Corp. --> <link rel="stylesheet" type="text/css" href="./ibmdita.css" /> <link rel="stylesheet" type="text/css" href="./ic.css" /> <title>Just-In-Time compiler</title> </head> <body id="jit"><a name="jit"><!-- --></a> <!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script> <h1 class="topictitle1">Just-In-Time compiler</h1> <div><p>A Just-In-Time (JIT) compiler is a platform-specific compiler that generates machine instructions for each method as needed.</p> <p>For more information about using the JIT compiler, and about the difference between the JIT compiler and direct processing, see the following pages:</p> <blockquote> <p><a href="runtperf.htm">Java™ runtime performance considerations</a>.</p> <p><a href="jitde.htm">Comparison of the JIT compiler and direct processing</a>.</p> </blockquote> <div class="note"><span class="notetitle">Note:</span> The default setting for <span class="keyword">i5/OS™</span> is to interpret (not compile) Java methods by using the Mixed-Mode Interpreter (MMI). MMI profiles each Java method as it interprets it. After reaching the threshold specified by the os400.jit.mmi.threshold property, MMI then specifies that <span class="keyword">i5/OS</span> use the JIT compiler to compile the method.</div> <p>For more information, see the entries for the java.compiler property and the os400.jit.mmi.threshold property in the appropriate list of Java system properties:</p> <blockquote> <p><a href="sysprop2.htm">Java system properties for Java 2 SDK (J2SDK), Standard Edition</a></p> </blockquote> </div> <div> <ul class="ullinks"> <li class="ulchildlink"><strong><a href="jitde.htm">Comparison of Just-In-Time compiler and direct processing</a></strong><br /> If you are trying to decide whether to use the Just-In-Time compiler or direct processing mode to run your Java program, this table provides additional information to help you make the best choice for your situation.</li> </ul> <div class="familylinks"> <div class="parentlink"><strong>Parent topic:</strong> <a href="runtperf.htm" title="Understanding the following considerations can help you improve the performance of your Java applications.">Java performance considerations</a></div> </div> </div> </body> </html>