Why Can\'t JVM Match Go\'s Low GC Pauses?

Understanding JVM's Challenges in Achieving Go-Level GC Pauses

One of Go's most notable features is its ability to maintain GC pauses below 1ms. This has led some to question why JVM still struggles to achieve similar performance despite its long history.

Architectural Differences

Contrary to common belief, there are no fundamental architectural limitations preventing JVM from achieving Go-level GC pauses. The key distinction lies in the design choices made by the respective GC algorithms.

Go's Non-Compacting GC

Go utilizes a non-compacting GC that prioritizes pause time reduction. This comes at the expense of throughput and memory footprint as it allows for fragmentation and requires write barriers.

JVM's Compacting Generational GC

In contrast, JVM employs a compacting generational GC. This approach offers higher throughput and scalability by minimizing fragmentation and reducing reference updates during collections. However, it inevitably introduces higher pause times.

Trade-Offs

The different GC designs reflect different performance goals. Go's GC is optimized for minimal pause time while JVM's GCs prioritize throughput and memory efficiency.

Recent Advances in JVM GC

Despite these differences, significant progress has been made in reducing JVM GC pauses. OpenJDK 16 introduced ZGC, a GC featuring max pauses of less than 1ms and average pauses of 50µs. OpenJDK 17's Shenandoah GC also exploits similar techniques to achieve comparable results.

Alternatives

Besides these new low-pause JVM GCs, third-party vendors also offer solutions such as Azul's pauseless collector and IBM's metronome.

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