How has compressed oops changed in recent Java versions?

Compressed ordinary object pointers (oops) have undergone significant changes in recent Java versions to optimize memory usage and improve performance, particularly for 64-bit JVMs. Introduced as a feature in Java 6, the evolution of compressed oops has aimed to reduce the memory footprint of applications by using 32-bit references instead of 64-bit references, which is beneficial for applications that do not require a large heap size.

In recent versions, such as Java 11 and onwards, developers have observed enhancements in the way compressed oops are handled, including better performance tuning and smarter allocation strategies. This allows the JVM to manage memory more efficiently, leading to faster access times and reduced garbage collection pauses, particularly for applications with large object graphs.

Additionally, the activation of compressed oops is generally automatic when the heap size is under a certain threshold, making it easier for developers to benefit from these improvements without needing extensive configuration changes.