It's been a while since I paid attention to the relative speed of jSuneido versus cSuneido. I just realized that with my recent optimizations, jSuneido now runs the standard library test suite in pretty much the same time as cSuneido.
In some ways that's not surprising, the JVM is a sophisticated platform - the garbage collector is very fast and multi-threaded, the JIT compiles to optimized machine code, etc.
On the other hand, Java forces a lot more overhead than C++. Integers have to be boxed, classes can only be nested by reference not embedding, you can't use pointers, you can't allocate objects on the stack, and so on. It's impressive that the JVM can overcome these "drawbacks".
It's nice to reach this point. And a nice confirmation that I wasn't totally out to lunch deciding to use Java and the JVM to re-implement Suneido.
Of course, the real advantage of jSuneido over cSuneido is that the server is multi-threaded and will scale to take advantage of multiple cores.