Fastest way to run an interpreter from node.js?

I am writing a small web server in node.js, and I've managed to integrate a scripting language into it. Currently, it generates the code and feeds it into the interpreter through spawn, and quite frankly works like a charm. However, I am afraid that spawning a seperate process just to run the server-side code is a performance bottleneck. What would be the best approach to invoke the interpreter (one thought I had was somehow embedding the interpreter, but I really don't know)?

1) You can implement the interpreter in node directly, using javascript or any other language that node runs.

2) You can implement the interpreter in some native language and include it as a node addon: http://nodejs.org/api/addons.html