How to troubleshoot out of memory issues when the JVM is hanged and it is not possible to get a heap dump

Veröffentlichungsdatum: Jul 25, 2025

Aufgabe

GOAL

Get information about the Heap Usage thru object statistics analysis and diagnose the root cause of an out of memory issue. This can be useful when getting errors while taking a heap dump for example:

Dumping heap to /root/crash.hprof ...
Exception in thread "main" java.io.IOException: Premature EOF
at sun.tools.attach.HotSpotVirtualMachine.readInt(HotSpotVirtualMachine.java:292)
at sun.tools.attach.LinuxVirtualMachine.execute(LinuxVirtualMachine.java:199)
at sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:261)
at sun.tools.attach.HotSpotVirtualMachine.dumpHeap(HotSpotVirtualMachine.java:224)
at sun.tools.jmap.JMap.dump(JMap.java:247)
at sun.tools.jmap.JMap.main(JMap.java:142)

Schritte

When you are using Java Flight Recorder (JFR), the JFR will use an event settings file to check which event types to record. By default in JFR, there are two settings, "default" and "profile". The default setting is recommended for Continuous Recordings as it has very low overhead (typically less than 1% overhead). The profile setting has more events and useful when profiling the application. Oracle Java Mission Control tool allows the creation of different templates using the Flight Recording Template Manager. By default, heap statistics is disabled to reduce the impact on the performance of the flight recording. Since this feature will impact the performance by around 20% it is recommended that you verify this in a controlled environment before enabling this feature in Production.

To enable heap statistics

1. Go to Flight Recording Template Manager

2. Duplicate any existing configuration

3. Enable the heap statistics checkbox

4. Export .jfc file and refer to this file while running jcmd or -XX:StartFlightRecording option

In JFR, the "settings" parameter specifies the path and name of the event settings file, which is of type JFC and it has the ".jfc" extension. By default, the "default.jfc" file is used and it's located in JAVA_HOME/jre/lib/jfr directory.

Examples of how to perform the capture:
jcmd JFR.start settings=/path/to/jfc/file/heapstatistics.jfc

For more information on how to perform the capture please refer to:
How to take a flight recording (JFR) on a Mule instance running under Java HotSpot JVM
How to create an automatic Java Flight Recording (AFR) on Hotspot JVM versions 7 and 8

After following these steps you will be able to check Heap Contents and Top Growers

Nummer des Knowledge-Artikels

001114468

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