Chapter 1. Shenandoah garbage collector

Shenandoah is the low pause time garbage collector (GC) that reduces GC pause times by performing more garbage collection work concurrently with the running Java program. Concurrent Mark Sweep garbage collector (CMS) and G1, default garbage collector for Red Hat build of OpenJDK 21 perform concurrent marking of live objects.

Shenandoah adds concurrent compaction. Shenandoah also reduces GC pause times by compacting objects concurrently with running Java threads. Pause times with Shenandoah are independent of the heap size, meaning you will have consistent pause time whether your heap is 200 MB or 200 GB. Shenandoah is an algorithm for applications which require responsiveness and predictable short pauses.