JRuby Compiler Will Happen

Things have really been clicking along on JRuby. Tom has been knocking down Rails unit tests left and right, and more and more stuff is working. I found a nice little performance booster that gives us as much as 30-40% speed increase when starting up. Other folks have been working on updated YAML parsers, ActiveRecord-to-JDBC connectors, and in general helping us test JRuby in more and more scenarios. The future looks pretty good.


I am still far from satisfied with the performance of JRuby. Even with recent cleanup and minor optimizations, a basic CGI-servlet Rails request takes a second or two to process. Much, much longer than it should have to, especially considering we're not hitting a persistent store yet. With JRuby moving ever closer to its goal of C Ruby 1.8 compatibility, why not start looking at those performance issues in more depth?

First Time for Everything

I will admit, I've never written a compiler. Heck, until JRuby, I'd never worked on a language interpreter, much less written one. Of course, a lot has changed in a year, and I'm now one of the two people in the world who know the most about JRuby's internals. It has been quite a lesson in interpreter, language, and VM design...a lesson I've wanted to learn for the better part of my life.

I believe it is time for us to start exploring options for compiling JRuby to intermediate "JRuby bytecode" or to Java bytecode in many cases. Other dyn-typed langages for the JVM continue to hold their compilers up as a reason to choose something other than JRuby. I think JRuby's time has come.

I have been studying Ruby's AST, JRuby's implementation of its interpreter and core libraries, and the C Ruby code, and I am now confident we can do some level of compilation in the short term. The redesign of the core interpreter I committed last Fall has opened the door for more flexible traversal of the AST, including the ability to partially compile some scripts.

And So It Begins...

With Rails, Spring, Swing, IRB, and our other demos for JavaOne basically ready to go (ahead of schedule!), I will be spending the next week or two researching and exploring options for a preliminary Ruby compiler. I believe I can have something by JavaOne; something primitive, sure, but perhaps something that can provide numbers to go on. Stay tuned!
Written on April 27, 2006