Java 27 Reaches GA With The G1 Garbage Collector By Default Everywhere

Oracle christened Java 27 today with the OpenJDK 27 release reaching general availability (GA) status. With Java 27, the Garbage-First "G1" garbage collector is now enabled by default everywhere. Since JDK 9 there was the G1 garbage collector used by default in Java server environments while now it's proven robust enough to use as the default everywhere. Compared to the Serial collector, G1 should be delivering competitive throughput, latency, memory footprint, and start-up time across all heap sizes. JEP 523 for changing to G1 by default everywhere reads: "Since then, we have improved the G1 collector across all metrics, and testing shows that G1 is now competitive with Serial at all heap sizes. With our recent work to reduce synchronization (JEP 522), G1's maximum throughput is close to that of Serial. G1's maximum latencies have always been better than those of Serial, since G1 reclaims memory in the old generation via incremental garbage collections rather than full collections. Finally, in recent releases we have reduced G1's native memory usage to levels comparable to that of Serial. G1's performance is now sufficient to replace Serial in all situations in which the JVM would previously have selected Serial. It is time to stop selecting Serial by default in constrained environments. This will also make it easier to understand and reason about the JVM’s behavior." OpenJDK / Java 27 also adds support for Post-Quantum Hybrid Key Exchange for TLS 1.3, the newest preview of lazy constants, the seventh preview of structured concurrency support for Java, compact object headers by default, and the latest incubator on Java's Vector API. The compact object headers by default will reduce object headers from 96 bits down to 64 bits for improving deployment density, enhancing data locality, and reducing the heap size. Since JDK 24, the compact object headers have said to proven their stability and performance to make it the new default. More details on the Java 27 GA release via this morning's release announcement.