In recent years, the Shenandoah garbage collector (GC) has gained popularity in the Java community due to its low-pause time and high throughput characteristics. However, like any GC algorithm, Shenandoah might not provide the best performance out of the box for every application workload. In this blog post, we will explore how to fine-tune Shenandoah GC for specific Java application workloads to achieve optimal performance.

Table of Contents

• Introduction to Shenandoah GC
• Fine-tuning Shenandoah GC
• Profiling your application
• GC-related JVM flags
• Heap sizing considerations
• Conclusion

Introduction to Shenandoah GC

Shenandoah GC is a low-pause, concurrent garbage collector for the Java Virtual Machine (JVM). It leverages a technique called “concurrent evacuation”, which allows it to perform garbage collection concurrently with application threads, resulting in very short pause times. The goal of Shenandoah GC is to minimize the impact of garbage collection on application performance.

Fine-tuning Shenandoah GC

To fine-tune Shenandoah GC for specific Java application workloads, it is important to understand the characteristics of your application and how it interacts with the garbage collector. Here are some key factors to consider:

Profiling your application

Before diving into fine-tuning, it is crucial to profile your application using tools like Java Flight Recorder or VisualVM. This will help you identify any performance bottlenecks and understand how the garbage collector is affecting your application’s behavior.

GC-related JVM flags

Shenandoah GC provides a set of JVM flags that can be used to control its behavior. Some important flags to consider for fine-tuning include:

• XX:+UseShenandoahGC: Enables Shenandoah GC.
• XX:ShenandoahGCHeuristics: This flag allows you to select a specific heuristics mode suitable for your workload. Options include adaptive, static, and compact.
• XX:ShenandoahGCCycles: Determines the frequency and duration of GC cycles. Adjusting this flag can have a significant impact on pause times.
• XX:ShenandoahHeapRegionSize: Specifies the size of Shenandoah GC’s heap regions. Adjusting this flag can help optimize memory usage.

Heap sizing considerations

Properly sizing the heap for your application is crucial for achieving optimal performance. Shenandoah GC works best when the heap size is set to a value that allows for efficient evacuation. It is recommended to allocate enough heap space to accommodate your application’s working set, but not too much to avoid unnecessary overheads.

Conclusion

Fine-tuning Shenandoah GC for specific Java application workloads can significantly improve the overall performance and responsiveness of your application. By understanding your application’s behavior and utilizing the available JVM flags, you can optimize the garbage collection process and minimize its impact on your application. Remember to profile your application to identify any bottlenecks and experiment with different settings to find the best configuration for your workload.

#java #garbagecollector