Re:Eclipse OpenJ9 – Open-source JVM
by kuschku on Sunday September 17, 2017 @08:58AM
(#15269397)
That’s not an option, that was the whole point of the discussion.
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If changing the JVM spec is an option, then surely so is using an existing spec. IBM has an RTSJ JVM[1], which, I believe, is based on J9.
[1]: https://www.ibm.com/support/knowledgecenter/en/SSSTCZ_3.0.0/...
Changing the JVM spec has a chance at being applied in future normal JVMs. Using an entirely separate solution has not.
It's not an entirely separate solution, but a Java standard. In any event, it's probably overkill if all you need are acceptable pause-times for games (RTSJ is for hard-realtime, safety-critical systems, where even 2us jitter may kill someone). There are "pauseless" GCs for the JVM (with 1-10ms max pause, depending on the GC) without hard realtime guarantees. We just need more free implementations.
Eclipse OpenJ9's -Xgcpolicy:metronome is one of those GCs. Depending on how you well you configure your operating system, it defaults to 3ms pauses along with an application utilization contract.