5 ms·

The RTSJ solution is to simply pre-allocate everything you could ever want and reuse that. That’s horrible to use for game development.

merb 9y ago
I'm not a game developer, so why is that horrible? consider I have an array/map of my game objects and the rest only works with methods, so most stuff does not lie on the heap, well that means basically no strings, since they would add to heap memory aswell, but only using basic datatypes and arrays. why would some kind of that be problematic? I mean graphics programmic is kind of new to me, but considering that you could offload that to a c/c++ engine via jni (that's another horrible thing of some kind), but just the game code itself doesn't seems to be to bad, does it?
- kuschku 9y ago
  > why would some kind of that be problematic? I mean graphics programmic is kind of new to me, but considering that you could offload that to a c/c++ engine via jni (that's another horrible thing of some kind), but just the game code itself doesn't seems to be to bad, does it? The whole point is not to offload anything. If you need to offload anything, even the render loop, the language has failed.
pron 9y ago
> 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 9y ago
  > 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 9y ago
    You don't. You use an RTSJ JVM.
    - kuschku 9y ago
      That’s not an option, that was the whole point of the discussion.
      - pron 9y ago
        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/com.ibm.wrt.rtlinux.doc.30/homepage/plugin-homepage-rt.html https://www.ibm.com/support/knowledgecenter/en/SSSTCZ_3.0.0/...
        kuschku 9y ago
        Changing the JVM spec has a chance at being applied in future normal JVMs. Using an entirely separate solution has not.
        pron 9y ago
        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.
        mstoodle 9y ago
        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.
imtringued 9y ago
Isn't that what almost every game does during loading screens?

merb 9y ago

I'm not a game developer, so why is that horrible? consider I have an array/map of my game objects and the rest only works with methods, so most stuff does not lie on the heap, well that means basically no strings, since they would add to heap memory aswell, but only using basic datatypes and arrays. why would some kind of that be problematic? I mean graphics programmic is kind of new to me, but considering that you could offload that to a c/c++ engine via jni (that's another horrible thing of some kind), but just the game code itself doesn't seems to be to bad, does it?

kuschku 9y ago
> why would some kind of that be problematic? I mean graphics programmic is kind of new to me, but considering that you could offload that to a c/c++ engine via jni (that's another horrible thing of some kind), but just the game code itself doesn't seems to be to bad, does it? The whole point is not to offload anything. If you need to offload anything, even the render loop, the language has failed.

pron 9y ago

> 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 9y ago
> 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 9y ago
  You don't. You use an RTSJ JVM.
  - kuschku 9y ago
    That’s not an option, that was the whole point of the discussion.
    - pron 9y ago
      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/com.ibm.wrt.rtlinux.doc.30/homepage/plugin-homepage-rt.html https://www.ibm.com/support/knowledgecenter/en/SSSTCZ_3.0.0/...
      - kuschku 9y ago
        Changing the JVM spec has a chance at being applied in future normal JVMs. Using an entirely separate solution has not.
        pron 9y ago
        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.
        mstoodle 9y ago
        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.

imtringued 9y ago

Isn't that what almost every game does during loading screens?