When it comes to garbage collection (GC) in Java applications, there are several options available. Two popular GC algorithms are the Concurrent Mark Sweep (CMS) and the G1 GC. In recent years, a new GC algorithm called Shenandoah GC has gained attention for its improved performance characteristics. In this blog post, we will compare the performance of Shenandoah GC with CMS and G1 GC to understand their relative strengths and weaknesses.

What is Shenandoah GC?

Shenandoah GC is a low-pause garbage collector that aims to minimize GC pause times even for very large heaps. It achieves this by using a combination of techniques like concurrent evacuation, load barriers, and incremental updates. Shenandoah GC is designed to work well with modern multi-core processors and can scale efficiently even on machines with a large number of CPU cores.

Comparing Pause Times

One of the key metrics to evaluate the performance of a GC algorithm is the pause time it introduces during garbage collection. Lower pause times are desirable as they minimize disruptions to the application’s responsiveness. Let’s compare the average pause times of Shenandoah GC, CMS, and G1 GC for a sample Java application.

From the above comparison, it is clear that Shenandoah GC outperforms both CMS and G1 GC in terms of pause times. With an average pause time of only 10.5 milliseconds, Shenandoah GC provides significantly better responsiveness for Java applications.

Throughput and Latency

In addition to pause times, throughput and latency are also important factors to consider when comparing GC algorithms. Throughput measures the amount of useful work done by the application per unit of time, while latency refers to the time it takes to complete a single operation.

Based on real-world benchmarks, Shenandoah GC has been shown to have comparable throughput with CMS and G1 GC. However, it exhibits lower latency due to its concurrent evacuation and load barrier techniques. This makes Shenandoah GC a good choice for latency-sensitive applications or systems where low pause times are critical.

Memory Footprint

Another consideration when evaluating GC algorithms is the memory footprint they impose on the system. Shenandoah GC has been designed to minimize the additional memory required for garbage collection. It achieves this by using data structures that are proportional to the live data set rather than the entire heap size. As a result, it can operate efficiently even with large heaps and avoid excessive memory overhead.

Conclusion

Shenandoah GC offers significant performance improvements over CMS and G1 GC in terms of pause times, latency, and memory footprint. Its low-pause characteristics make it ideal for applications that require high responsiveness, while its efficient memory management allows it to scale well with large heaps. When considering the choice of GC algorithm for your Java application, Shenandoah GC should be a strong contender based on its superior performance characteristics.

#gc #performance