Garbage Collection in Java: The progress since JDK 8 by Stefan Johansson

Significant performance improvements have been made in Java GC since JDK 8, with G1 becoming the default collector in JDK 9

There are now 5 main garbage collectors in OpenJDK: Serial (low memory overhead), Parallel (high throughput), G1 (balanced performance), ZGC and Shenandoah (ultra-low latency)

Generational garbage collection was added to ZGC in JDK 21, becoming default in JDK 23, providing 15-40% performance improvements

Real-world success stories (Netflix, Mercado Libre) show significant benefits from upgrading from JDK 8 to newer versions:

• 20-40% throughput improvements
• 25-50% reduction in memory usage
• 30-50% reduction in latency

Key GC improvements between JDK 8 and 21:

• Streamlined threading systems
• More efficient remember set implementations
• Better native memory management
• Reduced pause times

G1 collector improvements include:

• Default pause target of 200ms
• Mixed collections capability
• Better throughput compared to JDK 8
• More efficient memory usage

For most applications over 4GB heap size, G1 is recommended as the default choice

ZGC shows best performance for ultra-low latency requirements and large heaps, especially with the new generational mode

Upgrading from JDK 8 to newer versions (especially 17 or 21) is highly recommended for significant performance gains

Future focus areas include further latency improvements, footprint optimization, and better integration with Project Loom