Startup is too slow, largely because the invocation methods we generate have to be classloaded and verified. One proven way to reduce startup time is to lazily initialize those classes. In addition, this shows significant gains even for reflected code. Add lazy initialization to the runtime, on by default (and we'll see if there's any problems with doing that). Provide a system property that can be set to false to disable lazy init (jruby.stubs.lazy=false).