In this blog post, we will explore how the Shenandoah Garbage Collector (GC) handles reference processing and weak references. Shenandoah GC is a low-pause garbage collector designed for large heaps, with a focus on minimizing pause times.

What is reference processing?

Reference processing is the mechanism used by the garbage collector to trace and update object references. When the GC identifies an object as garbage, it needs to make sure that any references pointing to that object are properly updated or invalidated.

Shenandoah GC uses a concurrent reference processing algorithm to minimize pause times and ensure efficient garbage collection.

Concurrent reference processing

Shenandoah GC performs reference processing concurrently with the running application threads. This means that reference updates happen in parallel with the application’s execution, reducing the impact of GC pauses on the overall performance.

By performing reference processing concurrently, Shenandoah GC ensures that the application can continue running with minimal interruption, resulting in improved responsiveness and throughput.

Handling weak references

Weak references are special types of references that do not prevent the referenced object from being garbage collected. They are commonly used for implementing caches, event listeners, and other scenarios where it’s desirable to have a reference that automatically becomes invalid when the referenced object is no longer needed.

Shenandoah GC handles weak references efficiently by scanning and updating them concurrently with the reference processing phase. This allows the GC to identify and invalidate weak references to garbage objects, freeing up memory without impacting the running application.

Conclusion

Shenandoah GC’s approach to reference processing and weak references provides several benefits, including reduced pause times and efficient handling of weak references. By performing reference processing concurrently, Shenandoah GC ensures that the garbage collection process is seamless and transparent to the application.

If you are working with large heaps and aim for low-pause garbage collection, Shenandoah GC is a compelling choice. Its ability to handle reference processing and weak references effectively contributes to its overall performance and responsiveness.

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