IntelliJ IDEA 2021.2 Help

Java Flight Recorder

Java Flight Recorder (JFR) is a monitoring tool that collects information about the events (pieces of data) in a particular instant of time in a Java Virtual Machine during the execution of an application.

Java Flight Recorder is supported natively in the following JDK builds:

  • Oracle JDK 8-10: provided that the UnlockCommercialFeatures VM option is enabled

  • Oracle JDK 11 and later

  • OpenJDK 11 and later

Enable JFR for Oracle JDK 8 or later

  1. From the main menu, select Run | Edit Configurations and from the list on the left, select the run configuration that you want to analyze with JFR.

  2. To the VM options field, add the following line: -XX:+UnlockCommercialFeatures.

  3. Apply the changes and close the dialog.

Enabling JFR

JFR configurations

There are two pre-installed configurations: Default and Profile. The Default configuration has low overhead (about 1%). That's why it works well for continuous profiling. The Profile configuration has overhead about 2% and can be used for more detailed application profiling.

These configurations cover most use cases. You can select the most suitable configuration in Settings/Preferences | Build, Execution, Deployment | Java Profiler | Java Flight Recorder.

JFR configurations

If the pre-defined configurations don't meet your needs, you can create and upload your own settings by means of Java Mission Control.

Create a custom JFR configuration (optional)

  1. Run Java Mission Control that you can find in JAVA_HOME/bin/jmc or download from https://jdk.java.net/jmc/.

  2. From the Java Mission Control main menu, select Window | Flight Recording Template Manager.

  3. Click Import Files on the panel on the right and select one of the pre-installed configurations in the .jfc format:

    • For Java 10 and earlier: JAVA_HOME/jre/lib/jfr/

    • For Java 11 and later: JAVA_HOME/Contents/Home/lib/jfr/

  4. Select Edit | Advanced, change the necessary settings, and click OK.

  5. In the Flight Recording Template Manager dialog, click Export File.

  6. Specify another name for the new settings file and change its location if necessary. Click Save.

For more information on how to configure custom settings, refer to Controlling Recording Data by Using Templates.

Load the custom configuration to the IDE (optional)

  1. In the Settings/Preferences dialog Ctrl+Alt+S, select Build, Execution, Deployment | Java Profiler.

  2. Select the Java Flight Recorder profiling configuration to which you want to load your custom settings or create a new configuration by clicking the Add button.

  3. In the Profiling Settings area, select the Custom settings file option and click the Browse button.

  4. Specify the path to the custom settings file and click Open.

  5. Apply the changes and close the Settings/Preferences dialog.

Uploading custom settings to JFR
Last modified: 26 August 2021