Java Virtual Threads: A Case Study

Java Virtual Threads, introduced in JDK 21, offer a new lightweight, scalable approach to concurrency. However, they do not present clear advantages over Open Liberty's existing autonomic thread pool for typical cloud-native Java workloads. Performance evaluations revealed that while virtual threads ramp up faster, their CPU throughput is generally lower for CPU-intensive tasks. Memory footprint benefits are inconsistent and can be outweighed by other JVM memory usages. Some unexpected performance issues due to interactions with the Linux kernel and ForkJoinPool were also observed.