Explaining java.lang.OutOfMemoryError: PermGen space

Thu, 05/19/2005 - 07:00.

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Most probably, a lot of Java developers have seen OutOfMemory error one time or other. However these errors come in different forms and shapes. The more common is: "Exception in thread "main" java.lang.OutOfMemoryError: Java heap space" and indicates that the Heap utilization has exceeded the value set by -Xmx. This is not the only error message, of this type, however.

One more interesting flavor of the same error message, less common but hence even more troublesome is: "java.lang.OutOfMemoryError: PermGen space". Most of the memory profiler tools are unable to detect this problem, so it is
even more troublesome and therefor - interesting.

To understand this error message and fix it, we have to remember that, for optimized, more efficient garbage-collecting Java Heap is managed in generations - memory segments holding objects of different ages. Garbage collection algorithms in each generation are different. Objects are allocated in a generation for younger objects - the Young Generation, and because of infant mortality most objects die there. When the young generation fills up it causes a Minor Collection. Assuming high infant mortality, minor collections are garbage-collected frequently. Some surviving objects are moved to a Tenured Generation. When the Tenured Generation needs to be collected there is a Major Collection that is often much slower because it involves all live objects. Each generation contains variables of different length of life and different GC policies are applied to them.

There is a third generation too - Permanent Generation. The permanent generation is special because it holds meta-data describing user classes (classes that are not part of the Java language). Examples of such meta-data are objects describing
classes and methods and they are stored in the Permanent Generation. Applications with large code-base can quickly fill up this segment of the heap which will cause java.lang.OutOfMemoryError: PermGen no matter how high your -Xmx and how much memory you have on the machine.

Sun JVMs allow you to resize the different generations of the heap, including the permanent generation. On a Sun JVM (1.3.1 and above) you can configure the initial permanent generation size and the maximum permanent generation size.

To set a new initial size on Sun JVM use the -XX:PermSize=64m option when starting the virtual machine. To set the maximum permanent generation size use -XX:MaxPermSize=128m option. If you set the initial size and maximum size to equal values you may be able to avoid some full garbage collections that may occur if/when the permanent generation needs to be resized. The default values differ from among different versions but for Sun JVMs upper limit is typically 64MB.

Some of the default values for Sun JVMs are listed below.

JDK 1.3.1_06	Initial Size	Maximum Size
Client JVM	1MB	32MB
Server JVM	1MB	64MB

JDK 1.4.1_01	Initial Size	Maximum Size
Client JVM	4MB	64MB
Server JVM	4MB	64MB

JDK 1.4.2	Initial Size	Maximum Size
Client JVM	4MB	64MB
Server JVM	16MB	64MB

JDK 1.5.0	Initial Size	Maximum Size
Client JVM	8MB	64MB
Server JVM	16MB	64MB

Following is a JSP code you can use to monitor memory utilization in different generations (including PermGen):

As of JBoss v3.2.8/4.0.2, the ServerInfo MBean registered under the name
jboss.system:type=ServerInfo has been enhanced with a new operation
listMemoryPools(boolean fancy) that presents information about the
memory pools managed by the JVM.

Thank you for valuable

Submitted by bhavani (not verified) on Wed, 07/16/2008 - 13:35.

Thank you for valuable information.
It is very useful to me in my project.
JSP Page is very good.

Thank you , I search the web

Submitted by Boris (not verified) on Sun, 08/10/2008 - 09:57.

Thank you , I search the web quite a lot for this topic and your explanation was the most usefull one

Thanks

Submitted by Kyle (not verified) on Fri, 09/19/2008 - 18:54.

Thanks for the code, however there was an error.

Here is the correct code:

<%@ page import="java.lang.management.*" %>
<%@ page import="java.util.*" %>

JVM Memory Monitor

<%
Iterator iter = ManagementFactory.getMemoryPoolMXBeans().iterator();

while (iter.hasNext())
{
MemoryPoolMXBean item = (MemoryPoolMXBean) iter.next();
%>

Memory MXBean
Heap Memory Usage<%=
ManagementFactory.getMemoryMXBean().getHeapMemoryUsage()
%>
Non-Heap Memory
Usage<%=
ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage()
%>
<%} %>

Memory Pool MXBeans
<%
iter = ManagementFactory.getMemoryPoolMXBeans().iterator();
while (iter.hasNext())
{
MemoryPoolMXBean item = (MemoryPoolMXBean) iter.next();
%>

<%= item.getName() %>
Type<%= item.getType() %>
Usage<%= item.getUsage() %>
Peak Usage<%= item.getPeakUsage() %>
Collection Usage<%= item.getCollectionUsage() %>

<%
}

another implementation

Submitted by Paul Mietz Egli (not verified) on Wed, 09/24/2008 - 19:33.

Thanks for the article! If your a JSP-XML syntax junkie like me, here's another implementation of the memory monitor page:

<jsp:root version="1.2" xmlns:jsp="http://java.sun.com/JSP/Page"
  xmlns:c="http://java.sun.com/jsp/jstl/core"
  xmlns:fmt="http://java.sun.com/jsp/jstl/fmt"
  >

  <jsp:directive.page contentType="text/html" />
  <jsp:directive.page import="java.lang.management.*"/>
  <jsp:directive.page import="java.util.*"/>


<html>
  <head>
    <title>JVM Memory Monitor</title>
    <style type="text/css">
      td {
        text-align: right;
      }
    </style>
  </head>
<body>
  <jsp:scriptlet>
    MemoryMXBean memoryBean = ManagementFactory.getMemoryMXBean();
    pageContext.setAttribute("memoryBean", memoryBean);
  
    List<MemoryPoolMXBean> poolBeans = ManagementFactory.getMemoryPoolMXBeans();
    pageContext.setAttribute("poolBeans", poolBeans);
  </jsp:scriptlet>

  <h3>Total Memory</h3>
  <table border="1" width="100%">
    <tr>
      <th>usage</th>
      <th>init</th>
      <th>used</th>
      <th>committed</th>
      <th>max</th>
    </tr>
    <tr>
      <td style="text-align: left">Heap Memory Usage</td>
      <td><fmt:formatNumber value="${memoryBean.heapMemoryUsage.init / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      <td><fmt:formatNumber value="${memoryBean.heapMemoryUsage.used / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      <td><fmt:formatNumber value="${memoryBean.heapMemoryUsage.committed / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      <td><fmt:formatNumber value="${memoryBean.heapMemoryUsage.max / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
    </tr>
    <tr>
      <td style="text-align: left">Non-heap Memory Usage</td>
      <td><fmt:formatNumber value="${memoryBean.nonHeapMemoryUsage.init / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      <td><fmt:formatNumber value="${memoryBean.nonHeapMemoryUsage.used / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      <td><fmt:formatNumber value="${memoryBean.nonHeapMemoryUsage.committed / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      <td><fmt:formatNumber value="${memoryBean.nonHeapMemoryUsage.max / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
    </tr>
  </table>

  <h3>Memory Pools</h3>
  <table border="1" width="100%">
    <tr>
      <th>name</th>
      <th>usage</th>
      <th>init</th>
      <th>used</th>
      <th>committed</th>
      <th>max</th>
    </tr>
    <c:forEach var="bean" items="${poolBeans}">
      <tr>
        <td style="text-align: left">${bean.name}</td>
        <td style="text-align: left">Memory Usage</td>
        <td><fmt:formatNumber value="${bean.usage.init / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
        <td><fmt:formatNumber value="${bean.usage.used / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
        <td><fmt:formatNumber value="${bean.usage.committed / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
        <td><fmt:formatNumber value="${bean.usage.max / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      </tr>
      <tr>
        <td></td>
        <td style="text-align: left">Peak Usage</td>
        <td><fmt:formatNumber value="${bean.peakUsage.init / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
        <td><fmt:formatNumber value="${bean.peakUsage.used / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
        <td><fmt:formatNumber value="${bean.peakUsage.committed / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
        <td><fmt:formatNumber value="${bean.peakUsage.max / (1024 * 1024)}" maxFractionDigits="1"/> Mb</td>
      </tr>
    </c:forEach>
  </table>

</body>
</html>

-paul

Hi I tried to use your code,

Submitted by Anonymous (not verified) on Tue, 09/29/2009 - 10:51.

Hi I tried to use your code, but there is an error:

The element type "MemoryPoolMXBean" must be terminated by the matching end-tag "".

Syntax error

Submitted by Matthias (not verified) on Fri, 07/30/2010 - 15:35.

There's a syntax error in this code. Code inside <jsp:scriptlet> must have < and > escaped, such as in: List<MemoryPoolMXBean&gt. Also at the end you need a closing tag </jsp:root>,

Finally, as this is using JSTL, you will want to deploy this inside a Web App that has agood web.xml Deployment descriptor such as
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4" > <welcome-file-list> <welcome-file>index.jsp </welcome-file-list> </web-app>
and make sure that JSTL is deployed / available in the container. For WebLogic 10.3.3 where I tried this on, this means deploying "C:\bea10.3.3\wlserver_10.3\common\deployable-libraries\jstl-1.2.war" as a library, then referencing this in WEB-INF/weblogic.xml as in
<?xml version='1.0' encoding='UTF-8'?> <weblogic-web-app xmlns="http://www.bea.com/ns/weblogic/weblogic-web-app" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.bea.com/ns/weblogic/weblogic-web-app http://www.bea.com/ns/weblogic/weblogic-web-app/1.0/weblogic-web-app.xsd" > <library-ref> <library-name>jstl <specification-version>1.2 <implementation-version>1.2 <exact-match>false </library-ref>

</weblogic-web-app>
Then the page shows up. Maybe there's an easier way, but above works for me. Thought i'd share this back.

Thank you for good

Submitted by Ra Josse (not verified) on Wed, 01/07/2009 - 18:19.

Thank you for good explanation and write-up. Although I am naive in this area, I was able to understand
this java.lang.OutOfMemoryError: PermGen space error.

Hey, thanks for your useful

Submitted by Anonymous (not verified) on Thu, 03/12/2009 - 06:06.

Hey, thanks for your useful post.

Good explaination in very few words

Submitted by Harish Kumar (not verified) on Mon, 03/16/2009 - 19:11.

This is a good explaination of variuos generations in few words. This is really helpful. Thanks for putting it here.

PermGen space

Submitted by Charles (not verified) on Tue, 04/14/2009 - 14:01.

Hi folks,

This JSP page is awesome. However, is it possible to find out what is invoking those peaks ?

It would be cool to handle those peaks and optimize our code to avoid this kind of problem.

Thanks

Charles

PermGen space

Submitted by Rakesh Sinha (not verified) on Mon, 05/04/2009 - 12:46.

Very nice and useful article. Thank you very much.

Java profiler tools for analysing PermGen space

Submitted by Srihari Konakanchi (not verified) on Fri, 06/12/2009 - 16:41.

Very good explanation!
can you please let us know which profilers can be used to analyse OutOfMemory PermGen space issue?

Srihari Konakanchi

Thanks for your best answer

Submitted by Shreyas (not verified) on Tue, 06/16/2009 - 07:59.

This is the best answer I have come accross.
You have provide the detail explanation.
Thanks for your answer.
Keep it up.

its a very good solution,

Submitted by Rohit Bhangur (not verified) on Thu, 06/18/2009 - 10:11.

its a very good solution, thanks for your help.

Thanks a lot for that JSP code

Submitted by Rob (not verified) on Wed, 07/01/2009 - 09:37.

Thanks a lot for that JSP code. I have been trying for 2 or 3 days to see how much JVM heap space was being used and this is the first time I have found a program that I can actually get to work.

Thanks again!

Nice Expalnation

Submitted by Vikas (not verified) on Thu, 07/23/2009 - 11:51.

Very minutely explained in few words --------------------appriciative

This article is extremely

Submitted by Anonymous (not verified) on Tue, 08/04/2009 - 23:59.

This article is extremely clear and useful. Format-wise, however, I don't understand the purpose of the wide verticle grey strip along the left side of the page. It gets in the way.

Huge thanks for the useful

Submitted by StevenG (not verified) on Wed, 10/28/2009 - 20:44.

Huge thanks for the useful article. This error is a real pain for me for quite a long time. I though that "java.lang.OutOfMemoryError: PermGen space" is the end of the road. I mean when I was facing this error, my work was over at this point because I didn't actually know what to do and what the hell this error means. But after reading your great article everything is all right now. Thanks one more time and I will be looking forward to another great ones from you.

Sincerely,

Steven Gorrson from java software development

Thanks!

Submitted by Anonymous (not verified) on Wed, 11/18/2009 - 17:47.

Awesome write-up. Would love an edit to include Java 1.6.

Thanks Again!

This JSP page is awesome.

Submitted by mrktlr (not verified) on Sat, 11/27/2010 - 10:27.

This JSP page is awesome. However, is it possible to find out what is invoking those peaks ? It would be cool to handle those peaks and optimize our code to avoid this kind of problem.

Mark Taylor
Thanks

Error in Tomcat 6

Submitted by James Wright (not verified) on Tue, 12/29/2009 - 15:02.

I was getting the PermGen error in Tomcat 6. I add the MaxPermSize setting and have not gotten the error again. Here is the line to add to the catalina.sh file:

export JAVA_OPTS="-Xmx1024m -XX:MaxPermSize=256m"

Thanks

Submitted by jrhooker (not verified) on Tue, 03/02/2010 - 22:35.

Adding my voice to the chorus of thanks; this was really useful and clearly written. Thanks for taking the time.

Good explanation on the

Submitted by Anonymous (not verified) on Thu, 05/27/2010 - 07:06.

Good explanation on the point.
It was very useful to understand the things better

Thank you for sharing


<%@ page import="java.lang.management.*" %>

<%@ page import="java.util.*" %>
<h1 style="text-decoration: underline;">JVM Memory Monitor</h1>
<h2>Memory MXBean</h2>

<b>Heap Memory Usage:</b> <%= ManagementFactory.getMemoryMXBean().getHeapMemoryUsage() %><br>

<b>Non-Heap Memory Usage: </b><%= ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage() %><br>
<h2>Memory Pool MXBeans</h2>

<%

	Iterator iter = ManagementFactory.getMemoryPoolMXBeans().iterator();
	while (iter.hasNext()) {

		MemoryPoolMXBean item = (MemoryPoolMXBean) iter.next();

%>
		<div style="border-bottom: 1px solid #000000">

		<b>- Name:</b> <%= item.getName() %><br>

		<b>- Type:</b> <%= item.getType() %><br>

		<b>- Usage:</b> <%= item.getUsage() %><br>

		<b>- Peak Usage:</b> <%= item.getPeakUsage() %><br>

		<b>- Collection Usage:</b> <%= item.getCollectionUsage() %><br>

		</div>

<%

	}

%>

Explaining java.lang.OutOfMemoryError: PermGen space

Thank you for valuable

Thank you , I search the web

Thanks

another implementation

Hi I tried to use your code,

Syntax error

Thank you for good

Hey, thanks for your useful

Good explaination in very few words

PermGen space

PermGen space

Java profiler tools for analysing PermGen space

Thanks for your best answer

its a very good solution,

Thanks a lot for that JSP code

Nice Expalnation

This article is extremely

Huge thanks for the useful

Thanks!

This JSP page is awesome.

Error in Tomcat 6

Thanks

Good explanation on the

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Your explanations of Java

The monitoring page

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