In this blog post, we will explore two important aspects of the Shenandoah Garbage Collector (GC): Concurrent Marking Stats and Concurrent Marking Work Queues. These features contribute to the effectiveness and efficiency of the Shenandoah GC in managing memory in large-scale Java applications.
Table of Contents
Concurrent Marking Stats
The Concurrent Marking Stats feature in Shenandoah GC provides valuable insights into the marking process. It helps monitor the progress and efficiency of the concurrent marking phase during garbage collection.
Concurrent marking is the process where Shenandoah traverses the object graph to identify objects that are still reachable and should not be reclaimed. It is performed concurrently with the running application threads, minimizing the pause time for garbage collection.
With the Concurrent Marking Stats, you can gather information such as the number of objects marked, the time taken for marking, and the rate of marking progress. These statistics help you analyze the performance and identify potential areas for optimization in your Java application.
To enable Concurrent Marking Stats in Shenandoah GC, you can use the following JVM options:
-XX:+UnlockExperimentalVMOptions
-XX:+ShenandoahConcurrentMarkingStats
Concurrent Marking Work Queues
The Concurrent Marking Work Queues feature in Shenandoah GC is responsible for managing the marking work performed by concurrent threads during garbage collection.
Shenandoah divides the marking work into small tasks and distributes them among worker threads to maximize parallelism. These work queues ensure efficient workload distribution and prevent contention among threads.
By assigning tasks to different worker threads, Shenandoah effectively utilizes all available CPU resources for the concurrent marking process. This helps reduce the pause times and improves the overall performance of the garbage collection operation.
Furthermore, the Concurrent Marking Work Queues feature allows you to monitor the number of tasks issued, completed, and pending within the marking work queues. This information can provide insights into the efficiency of the marking process and help optimize the concurrency settings for your application.
To enable Concurrent Marking Work Queues in Shenandoah GC, you can use the following JVM options:
-XX:+UnlockExperimentalVMOptions
-XX:+ShenandoahConcurrentMarkingWorkQueues
Conclusion
Concurrent Marking Stats and Concurrent Marking Work Queues are crucial features in Shenandoah GC that contribute to its efficiency and effectiveness in managing memory in large-scale Java applications. By enabling these features and monitoring their statistics, you can gain valuable insights into the garbage collection process and optimize the performance of your application.
Keep in mind that Shenandoah GC is an experimental garbage collector, and you should carefully evaluate its suitability for your specific use case and workload. However, these features can potentially be instrumental in improving the overall garbage collection performance in certain scenarios.
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