Why Can Go Achieve Sub-1ms GC Pauses While JVM Lags Behind?

Why Can Go Achieve Sub-1ms GC Pauses While JVM Lags Behind?

Go's remarkable achievement of reducing garbage collection (GC) pauses to sub-1ms has left many JVM users wondering why their platform has not followed suit. This article delves into the architectural constraints that may prevent JVM GCs from reaching Go's levels of pause time reduction.

Historically, JVM users have faced significant challenges with high GC pauses. However, it's worth noting that there are indeed JVM GCs with low pause times, such as ZGC (introduced in OpenJDK 16) and Shenandoah (introduced in OpenJDK 17), which boast max pause times of under 1ms and average pause times of approximately 50µs.

Comparing GoGC and JVM GCs, we find that their low-pause approaches differ. GoGC is a non-compacting, non-generational collector that utilizes write barriers. This prioritization of pause time optimization results in trade-offs in performance, scalability, and memory footprint.

In contrast, JVM GCs like CMS (Concurrent Mark Sweep) are compacting generational collectors. They offer higher throughput by employing bump pointer allocation and reducing GC overhead. However, these optimizations can lead to longer pause times and potential fragmentation issues.

Furthermore, JVM GCs often aim to achieve multiple performance goals without compromising overall scalability. This balance approach presents challenges in maximizing pause time reduction.

In summary, while JVM GCs have made progress in reducing pause times, they still face limitations due to their different architectural design and focus on a broader spectrum of performance objectives. GoGC, on the other hand, sacrifices other performance metrics to prioritize low pause times specifically. It remains to be seen whether future JVM GC advancements can match or even surpass GoGC's impressive sub-1ms pause time achievement.

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