How does Shenandoah GC behave in multithreaded code?

Shenandoah Garbage Collector (GC) is a low-pause-time garbage collector for Java designed to minimize the impact of garbage collection on application throughput, especially in multithreaded environments. In multithreaded applications, Shenandoah achieves this by executing its marking and relocation phases concurrently with application threads, allowing for high levels of parallelism and lower pause times.

When using Shenandoah GC, the behavior in multithreaded code is as follows:

• Concurrent Marking: Shenandoah performs concurrent marking of live objects while application threads are still running, which helps in maintaining throughput.
• Relocation: During the relocation phase, Shenandoah also allows application threads to continue executing, reducing the time when threads are stopped.
• Heap Regions: Shenandoah uses a region-based memory management approach, where memory is divided into regions. This helps in managing memory allocation and collection in a scalable manner.
• Pause Time: Overall, the GC pauses are significantly shorter compared to traditional garbage collectors, making Shenandoah suitable for applications requiring low-latency responses.

Here's an example of how to enable Shenandoah GC in a Java application: