Unfortunately, our startup time is actually a bit worse than JRuby's. We end up having to essentially bootstrap two different runtimes, since JRuby+Truffle makes use of functionality from the main JRuby runtime. It's a known problem and we have concrete steps to take on improving the situation. It will get better, but you'll likely be disappointed with startup time today.

In addition to the steps we're taking, there's a sister project in Oracle Labs called the Substrate VM that would allow us to build a static binary with startup time on par with MRI. I can't speak to release plans or timelines on anything. I only mention it to show that startup time is a concern for us and we're thinking about how to fix it in a wide variety of ways.

Good to know work is being done there. Since not all of Ruby's use case is long running, startup time is pretty relevant for scripts.