Introduction

Garbage collection is an essential feature in Java that automatically manages memory by reclaiming objects that are no longer in use. Java 16 introduces an improved garbage collector that brings several enhancements to memory management and performance. In this blog post, we will explore the changes and improvements made to the garbage collector in Java 16.

ZGC - A Scalable Low-Latency Garbage Collector

Java 16 introduces the Z Garbage Collector (ZGC) as a production feature. ZGC is designed to provide consistent pause times, even with extremely large heaps. It is highly scalable and can handle heaps ranging from a few hundred gigabytes to multi-terabyte heaps.

With ZGC, the duration of garbage collection pauses is kept within a few milliseconds regardless of the heap size. This is achieved by using a concurrent garbage collector that performs collection work concurrently with the Java application’s execution.

Concurrent Thread-Local Handshakes

Java 16 introduces the concept of Concurrent Thread-Local Handshakes (CTLH) which allows the garbage collector to perform certain operations on potentially all threads running in the Java application. This feature enables better coordination between the garbage collector and the application threads, resulting in more efficient garbage collection.

CTLH provides a mechanism for threads to communicate with the garbage collector and participate in actions such as root scanning, object marking, or safe point operations. This helps reduce the overall pause times and improves application performance.

Performance Improvements

Java 16’s improved garbage collector brings noticeable performance improvements over previous versions. The ZGC performs better in terms of both throughput and latency compared to other garbage collectors like G1 and CMS. It reduces the impact of garbage collection pauses on application response times, making it suitable for latency-sensitive applications.

Additionally, the enhancements made to the garbage collector in Java 16 result in better memory utilization and reduced fragmentation. This leads to improved overall application performance and efficiency.

Conclusion

Java 16 introduces an improved garbage collector that brings significant enhancements to memory management and performance. The Z Garbage Collector (ZGC) provides consistent pause times, even with extremely large heaps, making it suitable for a wide range of applications. The introduction of Concurrent Thread-Local Handshakes (CTLH) enhances coordination between the garbage collector and application threads, further improving garbage collection efficiency. Overall, Java developers can benefit from the improved garbage collector in Java 16 for better performance and memory management.

References

• JEP 376: ZGC: Concurrent Thread-Stack Processing
• JEP 387: Elastic Metaspace
• ZGC: A Scalable Low-Latency Garbage Collector