With the release of Java 10, several enhancements have been made to the garbage collection (GC) mechanism. The GC in Java is responsible for reclaiming memory used by objects that are no longer in use, thereby preventing memory leaks and ensuring efficient memory usage. In this blog post, we will explore some of the improvements made to the GC in Java 10.

Parallel Full GC for the G1 Garbage Collector

One significant improvement in Java 10 is the introduction of parallel full GC for the Garbage First (G1) garbage collector. Previously, the G1 collector used a single-threaded approach for full garbage collection, which could be a performance bottleneck for applications with large heaps. With the new enhancement, the full GC phase can now take advantage of multiple threads, resulting in faster garbage collection times for large heaps.

To enable parallel full GC with the G1 collector, you can use the -XX:+ParallelFullGCThreads flag, specifying the number of threads to be used. For example, to use 4 threads for parallel full GC, you can add the following JVM argument:

java -XX:+UseG1GC -XX:+ParallelFullGCThreads=4 MyApp

Improved CMS Garbage Collector Ergonomics

The Concurrent Mark Sweep (CMS) garbage collector has also received improvements in Java 10. CMS is known for its low pause times, making it suitable for applications that require low latency. However, tuning the CMS collector for optimal performance has always been a complex task.

In Java 10, the CMS collector introduces new memory-related flags that simplify the process of tuning the collector. The -XX:CMSInitiatingOccupancyFraction flag allows you to set the initiating occupancy fraction, which triggers a concurrent marking cycle. Additionally, the -XX:CMSTriggerRatio flag defines the ratio of available CPU time for concurrent marking compared to the total time for a full GC.

By adjusting these flags, you can fine-tune the CMS collector to achieve the desired balance between pause times and overall throughput.

Conclusion

The enhancements made to the garbage collection mechanism in Java 10 provide developers with improved control over memory management and performance tuning. The introduction of parallel full GC for the G1 collector and the improved ergonomics of the CMS collector are significant milestones in making garbage collection more efficient and user-friendly.

By leveraging these enhancements, developers can optimize the performance of their Java applications and ensure efficient memory usage. As Java continues to evolve, we can expect further improvements in garbage collection and memory management in future releases.

For more information on Java 10 and its features, check out the official Java documentation.

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