Java 12 enhances G1 to automatically return Java heap memory to the operating system when idle. The mechanism introduced in Java 12 enables G1 to meet the pause time goal more often. But this could lead to G1 exceeding the pause-time goal if an application’s heuristics chose a collection set that was too large.Ī mechanism was needed to detect when heuristics repeatedly selected an incorrect amount of work for collections and, if this happened, have G1 perform collection work incrementally in steps, where the collection could be aborted after each step. Once the set had been determined and collection started, G1 collected all live objects in the regions of the collections in all regions without stopping. The result was a set of regions known as the collection set. Previously, an advanced analysis engine selected the amount of work to be done during a collection. A goal of G1 was to meet a user-supplied pause time target for its collection pauses. Java 12 makes G1 mixed collections abortable if they might exceed the pause target. Abortable mixed collections for the G1 garbage collector Red Hat currently supports Shenandoah on the Aarch64 and AMD64 architectures. The intent is not to fix all JVM pause issues, however. Shenandoah provides an appropriate algorithm for applications that value responsiveness and predictable short pauses.

Java 12 adds Shenandoah, an experimental garbage-collection algorithm, to reduce garbage-collection pause times by performing evacuation work concurrently with running of Java threads.

New features in Java 12 Shenandoah garbage collector

Java jdk 12