CODEWITHSUNDEEP
java
a.serghei
a.serghei

Reputation: 91

I need to monitor JVM Metaspace usage

I need to monitor JVM Metaspace usage. Can you help me please with the following things?

How can I find the metaspace size used ?

Using the following commands I found the maxmetaspace and the min metaspace :

jmap -heap `ps -ef | grep java | grep -v grep | awk '{print $2}'` | grep -i Metaspace

MetaspaceSize = 21807104 (20.796875MB)
MaxMetaspaceSize = 1073741824 (1024.0MB)

but how can I find what is the value of memory used right now ?

Upvotes: 9

Views: 12478

Answers (4)

Kire Haglin
Kire Haglin

Reputation: 7069

If you are using JDK 16, you can write a simple program to monitor your application using the new Remote streaming API. First start JMX on the host you want to monitor

$ jcmd <pid> ManagementAgent.start jmxremote.port=7091
             jmxremote.authenticate=false jmxremote.ssl=false

Then use the following program, which will print all metaspace events to standard out.

$ java MetaspaceMonitor.java localhost 7091

Source code:

import java.io.IOException;
import javax.management.MBeanServerConnection;
import javax.management.remote.JMXConnector;
import javax.management.remote.JMXConnectorFactory;
import javax.management.remote.JMXServiceURL;
import jdk.management.jfr.RemoteRecordingStream;

public class MetaspaceMonitor {
    public static void main(String... args) throws IOException {
        String host = args[0];
        Strin port = args[1];
        String url = "service:jmx:rmi:///jndi/rmi://" + host + ":" + port + "/jmxrmi";
        JMXServiceURL u = new JMXServiceURL(url);
        JMXConnector c = JMXConnectorFactory.connect(u);
        MBeanServerConnection connection = c.getMBeanServerConnection();
        try (var s = new RemoteRecordingStream(connection)) {
            s.enable("jdk.MetaspaceSummary");
            s.enable("jdk.MetaspaceGCThreshold");
            s.enable("jdk.MetaspaceAllocationFailure").withStackTrace();
            s.enable("jdk.MetaspaceOOM").withStackTrace();
            s.onEvent("jdk.MetaspaceSummary", System.out::println);
            s.onEvent("jdk.MetaspaceGCThreshold", System.out::println);
            s.onEvent("jdk.MetaspaceAllocationFailure", System.out::println);
            s.onEvent("jdk.MetaspaceOOM", System.out::println);
            s.start();
        }
    }
}

Upvotes: 0

Gunnar
Gunnar

Reputation: 18990

As of Java 11, the jcmd utility comes with a new command for displaying detailed metaspace information.

jcmd <PID> VM.metaspace

You can find an in-depth explanation in this post by Thomas Stuefe.

Alternatively, you can also use the JDK Flight Recorder (JFR) for metaspace monitoring, see the "Garbage Collections" view in JMC, and/or "Metaspace Summary" events in the event browser.

Upvotes: 1

Paolo Franzini
Paolo Franzini

Reputation: 61

I use jstat -gcutil <pid> | awk '{print($5)}' that prints the Metaspace utilization as a percentage of the space's current capacity.

there are further options for jstat, explained here:

http://docs.oracle.com/javase/8/docs/technotes/tools/unix/jstat.html

Upvotes: 4

Uli
Uli

Reputation: 1400

You can use the MemoryPoolMXBean.

List<MemoryPoolMXBean> memPool = ManagementFactory.getMemoryPoolMXBeans();
for (MemoryPoolMXBean p : memPool)
{
    if ("Metaspace".equals(p.getName()) 
    {
       ... here you have the memory pool mx bean with information about he metaspace
    }
}

Upvotes: 4

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