Tune the Performance of the Java Garbage Collector
Introduction
Overview
Setup
Types of Garbage Collector
Example Application
Basic GC Tuning Options
Intermediate GC Tuning Options
Review
Next Steps

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Check the JDK version

Different versions of the Java Development Kit (JDK) ship with different Garbage Collectors.

To check the version of Java installed on your system, run the following command:

    

        
        
            java --version

The output should look similar to:

    

        
        openjdk 21.0.4 2024-07-16 LTS
OpenJDK Runtime Environment Corretto-21.0.4.7.1 (build 21.0.4+7-LTS)
OpenJDK 64-Bit Server VM Corretto-21.0.4.7.1 (build 21.0.4+7-LTS, mixed mode, sharing)

If the java command is not recognized, you can follow the Arm Java install guide to install Java on your system.

Identify available Garbage Collectors

To find out the range of standard Garbage Collectors that are available for you to use, run the following command which prints the information:

    

        
        
            java -XX:+PrintFlagsFinal -version | egrep 'Use\w+GC'

The example output below shows that five GCs are available to use. The middle column shows the default value. Here you can see that the G1GC GC is enabled:

    

        
             bool UseAdaptiveSizeDecayMajorGCCost          = true                                      {product} {default}
     bool UseAdaptiveSizePolicyWithSystemGC        = false                                     {product} {default}
     bool UseDynamicNumberOfGCThreads              = true                                      {product} {default}
     bool UseG1GC                                  = true                                      {product} {ergonomic}
     bool UseMaximumCompactionOnSystemGC           = true                                      {product} {default}
     bool UseParallelGC                            = false                                     {product} {default}
     bool UseSerialGC                              = false                                     {product} {default}
     bool UseShenandoahGC                          = false                                     {product} {default}
     bool UseZGC                                   = false                                     {product} {default}

In the next section, you will learn about the different types of GCs.

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