I was going to say there's no way java programs boot in 0.1 seconds, but looked it up to be sure. Here's the results on my mac/i7, defaulted to server mode:

    $ time java HelloWorld
    Hello, world!

    real	0m0.101s

Touche. 0.1 seconds is exactly right, at least on my setup. That said, javac is slow given the program is 5 lines of code:

    $ time javac HelloWorld.java 

    real	0m0.511s
    user	0m0.833s
    sys	0m0.050s

And I'd ventured to guess that there must be something to the JIT being pretty slow for real-world applications, otherwise people wouldn't complain so frequently about it. Maybe aspects of JIT optimizations increase linearly-ish with the amount/complexity of code?

FWIW, we went with go at my work instead of java because our application is memory-intensive, and there's huge gains there in go over java.

A program that consists solely of println("Hello, World!"); is pretty stateless and trivial, there's not much that a JIT could do with this.

Somewhat anecdotally, I remember hearing Rich Hickey talking about how the JVM JIT loves stateless code. I'm pretty sure the vast majority of Java code in use is deeply stateful. I don't know how much of a difference this actually makes but it seemed like a relevant data point.

You are off by two orders of magnitude in the C case, at least with my trivial test case of writing hello world, and then a runner program that forks/execs/waitpids 10,000 times.

If you know what crt0.c does, you can see C is also pretty much the asymptote of what you're going to get from program startup, so it's a little silly to make the comparison.

Is that with the JVM already running or not?