The Zumwalt is using Real-Time Java, using a JVM from IBM that has an incremental GC with real-time guarantees (unlike the real-time Java spec, which essentiall

The Zumwalt is using Real-Time Java, using a JVM from IBM that has an incremental GC with real-time guarantees (unlike the real-time Java spec, which essentially works by disabling the GC for real-time threads, so their NonHeapRealTime threads were essentially an architected memory leak). IBM's Real-Time Java, with their real-time Metronome GC, is running on real-time Linux, for which I was the tech lead at the IBM Linux Technology Center. It was a fun project; since we were able to use the real-time Linux code base which Ingo Molnar and Stephen Rostedt worked on upstream, we spent most of our time stablizing the patches, and fed quite a few patches back upstream to get it into a production-ready state. Anyway, we had 50 microsecond interrupt and scheduler latency using real-time Linux, which allowed millisecond level real-time guarantees using garbage collected java threads.