Compact Object Headers
A HotSpot object-layout feature that reduces object-header size to lower heap footprint and improve memory density.
JVM Runtime Context
Compact Object Headers reduce HotSpot object-header size, improving heap density and potentially cache behavior in workloads dominated by many small objects. JDK 25 delivers the feature through JEP 519 as a production capability.
Measurement Boundary
A smaller header does not produce the same gain in every application. Object-size distribution, alignment, compressed-reference configuration, cache behavior, and the live-set shape determine the practical effect.
Related JVM Concepts
Source
- https://openjdk.org/jeps/519