Although not as a result of arrive till March 2021, Java Development Kit (JDK) 16 has begun to take form, with proposed options together with concurrent thread-stack processing for rubbish assortment, help for C++ 14 language options, and an “elastic metaspace” functionality to extra shortly return unused class metadata reminiscence to the OS.
JDK 16 would be the reference implementation of the model of ordinary Java set to observe JDK 15, which arrived September 15. The six-month launch cadence for normal Java would have JDK 16 arriving subsequent March.
As of September 24, 5 proposals formally goal JDK 16. Three different proposals — concurrent thread-stack processing and ports for Alpine Linux and Windows/Aarch64 — remained within the “proposed to target” stage.
The new capabilities coming to Java 16:
- Moving ZGC (Z Garbage Collector) thread-stack processing from safepoints to a concurrent section. Goals of this plan embrace eradicating thread-stack processing from ZGC safepoints; making stack processing lazy, cooperative, concurrent, and incremental; eradicating all different per-thread root processing from ZGC safepoints; and offering a mechanism for different HotSpot VM subsystems to lazily course of stacks. ZGC is meant to make GC pauses and scalability points in HotSpot a factor of the previous. So far, GC operations that scale with the dimensions of the heap and the dimensions of metaspace have been moved out of safepoint operations and into concurrent phases. These have included marking, relocation, reference processing, class unloading, and most root processing. The solely actions nonetheless accomplished in GC safepoints are a subset of root processing and a time-bounded marking termination operation. These roots have included Java thread stacks and different thread roots, with these roots being problematic as a result of they scale with the variety of threads. To transfer past the present scenario, per-thread processing, together with stack scanning, have to be moved to a concurrent section. With this plan, the throughput value of the improved latency ought to be insignificant and the time spent inside ZGC safepoints on typical machines ought to be lower than one millisecond.
- An elastic metaspace functionality, which returns unused HotSpot VM class metadata (metaspace) reminiscence extra promptly to the OS, reduces metaspace footprint and simplifies metaspace code to scale back upkeep prices. Metaspace has had points with excessive off-heap reminiscence use. The plan requires changing the prevailing reminiscence…
