This is the expected console output:
CompilerOracle: dontinline org/jruby/runtime/invokedynamic/InvokeDynamicSupport.invocationFallback
I'm not up to doing the tests but Charles claims to have seen some performance improvements, more interesting stuff here.
Anyway we may not have to wait too long for jruby-1.7.0 and theoretically at least, some significant performance improvements.
There might be an easier way to enter these settings see here by creating a file .jrubyc, which is essentially a "properties" file with entries such as:-
Use invokedynamic on Java 7+. Default is true.