JVM tuning tips for better performance with Shenandoah GC

10 Oct 2023

performance

The Java Virtual Machine (JVM) is a fundamental part of running Java applications, and optimizing its performance is essential for achieving better overall application performance. The Shenandoah garbage collector (GC) is a low-pause-time garbage collector introduced in JDK 12, aimed at reducing GC pause times and improving application throughput. In this article, we will explore some JVM tuning tips that can help in achieving better performance when using Shenandoah GC.

1. Enable Shenandoah GC

To take advantage of the benefits offered by Shenandoah GC, you need to enable it explicitly. Add the following JVM options to enable Shenandoah GC:

-XX:+UnlockExperimentalVMOptions
-XX:+UseShenandoahGC

2. Adjust Heap Size

Properly tuning the heap size is crucial for optimal performance. Shenandoah GC requires a minimum heap size of 32 MB, specified using the -Xms flag. You can set the maximum heap size using the -Xmx flag according to your application’s memory requirements. Consider monitoring the behavior of your application and adjusting the heap size accordingly to avoid frequent GC cycles.

-Xms32m
-Xmx512m

3. Control GC Threads

By default, Shenandoah GC uses the same number of garbage collector threads as Parallel GC. However, you can control the number of GC threads using the -XX:ParallelGCThreads flag. It is generally recommended to have fewer aggressive GC threads for better performance with Shenandoah GC.

-XX:ParallelGCThreads=4

4. Tune Shenandoah GC Settings

Shenandoah GC provides several additional tunable options to optimize its behavior based on your application’s needs. Some important settings include:

-XX:ShenandoahHeapCriticalPercent: Specifies the heap occupancy percentage at which evacuation pauses occur. Increasing this value can reduce the frequency of evacuation pauses.
-XX:ShenandoahMaxEvacuationPauseMillis: Sets the maximum desired evacuation pause time. Lower values reduce pause times but may result in increased CPU usage.
-XX:ShenandoahInitFreeThreshold: Sets the initial threshold for the amount of free space in the heap. Adjusting this value can help in controlling the growth rate of the heap.

Make sure to experiment and monitor the behavior of your application while tuning these settings to achieve the desired performance improvements.

5. Monitor and Analyze

Monitoring the behavior of your application and analyzing garbage collection patterns is essential for maximizing performance. Tools like JVisualVM, GCViewer, and JMX can provide insights into GC behavior, pause times, heap usage, and other critical metrics. Regularly monitor these metrics and use them to optimize your JVM configuration and application code.

By following these JVM tuning tips, you can leverage the features of Shenandoah GC to achieve better overall performance and reduced GC pause times in your Java applications.

#jvm #performance