[pron]

> The RTSJ solution is to simply pre-allocate everything you could ever want and reuse that.

That's not the RTSJ solution. RTSJ uses arenas, which are great if you have regular allocation/deallocation cycles, like, say, a frame in a game.

[kuschku]

> That's not the RTSJ solution. RTSJ uses arenas, which are great if you have regular allocation/deallocation cycles, like, say, a frame in a game.

So how do I get a user’s Oracle JRE installation to use arenas? The only realistic scenario is to preallocate and reuse.

[pron]

You don't. You use an RTSJ JVM.

[kuschku]

That’s not an option, that was the whole point of the discussion.

[pron]

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/...

[kuschku]

Changing the JVM spec has a chance at being applied in future normal JVMs. Using an entirely separate solution has not.

[pron]

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.