Date: Thu, 20 Feb 2003 00:36:43 -0800 From: Milo Hyson <milo@cyberlifelabs.com> To: Alexey Zelkin <phantom@FreeBSD.org.ua> Cc: FreeBSD Java Mailing List <freebsd-java@FreeBSD.ORG> Subject: Re: JVM choking Message-ID: <3E54939B.5080104@cyberlifelabs.com> References: <3E53A5DE.9080506@cyberlifelabs.com> <20030220001813.A51537@phantom.cris.net>
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[-- Attachment #1 --]
Alexey Zelkin wrote:
> Do you have testcases for anylizis ? I'd be interesting to take a look.
Yeah, see the attached file.
I've determined the problem to be an out-of-memory condition in the JVM
(if I wait long enough it spits out an exception). It's curious however
that the OS still reports having quite a lot of RAM free. I ran the
attached test code without any command-line arguments and had the
following results:
Test Case #1
------------
Athlon 1 GHz w/512 MB RAM
FreeBSD 4.7-RELEASE
Native JDK 1.3.1 w/Patchset 8
Died after 103000 entries, 277849 total nodes
140+ MB RAM still free according to the OS
Test Case #2
------------
Pentium II 400 MHz w/384 MB RAM
RedHat Linux 8
IBM JDK 1.4.1
Died after 461000 entries, 1029547 total nodes
60+ MB RAM still free according to the OS
It would appear that the memory manager in both JVMs is hitting some
sort of self-imposed limitation, as neither OS was anywhere near running
out of memory. Where exactly that limit is set seems to depend on which
JVM is used.
--
Milo Hyson
CyberLife Labs
> On Wed, Feb 19, 2003 at 07:42:22AM -0800, Milo Hyson wrote:
>
>>Has anyone run into any problems with their JVM choking on too many
>>objects? I'm currently working on an application in which 1,000,000+
>>objects are in existence at any given time. When the program first
>>starts up and begins creating the objects, things run very fast but soon
>>begin to slow down. Available memory also drops rapidly. Eventually,
>>everything grinds to a halt and it just sits there -- no disk activity,
>>no network traffic, no output, but 100% CPU load. Several tens of
>>megabytes of memory are still available so it's not out of RAM. After a
>>minute or so of no activity, an exception begins to be displayed but
>>never completes printing. There isn't enough of it shown to see what
>>kind of exception it is. At that point, all I can do is hit Ctrl-C
>>(which does kill it BTW).
>>
>>Anyone ever seen anything like this? I'm using the Native JDK 1.3.1
>>w/patchset 8. The problem occurs both with and without a JIT, but seems
>>to get further without it.
>>
>>--
>>Milo Hyson
>>CyberLife Labs
>>
>>
>>To Unsubscribe: send mail to majordomo@FreeBSD.org
>>with "unsubscribe freebsd-java" in the body of the message
>
>
>
[-- Attachment #2 --]
import java.util.*;
public class NodeTest
{
private static long totalNodes = 0;
private static long maxChildren = 0;
private Hashtable children;
private String name;
public NodeTest(String name)
{
totalNodes++;
children = new Hashtable(1);
this.name = name;
}
public void addChild(NodeTest child)
{
children.put(child.name,child);
if (children.size() > maxChildren)
maxChildren = children.size();
}
public NodeTest getChild(String name)
{
return (NodeTest)children.get(name);
}
public static void main(String args[])
{
// Default number of entries to add
long numEntries = 1000000;
// Default number of levels to create
int numLevels = 5;
// If there are any command-line arguments...
if (args.length >= 1)
{
try
{
// ...parse the first one into a Long
numEntries = Long.parseLong(args[0]);
}
catch (NumberFormatException e)
{
numEntries = 0;
}
// Make sure the number of entries is valid
if (numEntries <= 0)
{
System.err.println("Invalid number of entries");
System.exit(1);
}
// If there's a second argument...
if (args.length >= 2)
{
try
{
// ...parse it into an Integer
numLevels = Integer.parseInt(args[0]);
}
catch (NumberFormatException e)
{
numLevels = 0;
}
// Make sure the number of levels is valid
if (numLevels <= 0)
{
System.err.println("Invalid number of levels");
System.exit(1);
}
}
}
// Create a random-number generator
Random random = new Random();
// Create the root node
NodeTest rootNode = new NodeTest("<root>");
// For each entry...
for (long i=0; i<numEntries; i++)
{
NodeTest curNode = rootNode;
// Descend the levels
for (int j=0; j<numLevels; j++)
{
// Generate a random key
String key = "" + random.nextInt(50);
// Get or create an entry at that key
NodeTest child = curNode.getChild(key);
if (child == null)
{
child = new NodeTest(key);
curNode.addChild(child);
}
// Next level
curNode = child;
}
// Generate periodic status reports
if ((i % 1000) == 0)
System.out.println("Added " + i + " entries, totalNodes = " + totalNodes + ", maxChildren = " + maxChildren);
}
}
}
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