On May 15, 2011, at 5:36 PM, Charles Oliver Nutter wrote: > Can I get a rough guesstimate from the JVM guys how much more overhead > is involved in accessing a never-changed MutableCallSite versus a > ConstantCallSite? I have a few places where I want to use > invokedynamic to lazily initialize some literals. They'll never change > after the initial construction, but I can't create them in the > bootstrap because I need the state they pass in (e.g. the > org.jruby.Ruby instance they're associated with). I'd like to bind a > constant method handle into the site after the first call and never > change it again.
At this point, the overhead is nil, because we don't special-case CCS yet. :-( When we do a pass of performance tuning, we'll fix that, and then the overhead (MCS/CCS) is likely to be a memory reference or two, plus a branch. If you are building bytecodes which are specific to a particular org.jruby.Ruby instance, see if you can put a backpointer to the instance onto the Class containing the bytecodes, using ClassValue or a static field or a similar mechanism. Then you can access the Ruby instance in the BSM, and use a CCS. You are trying to do something pretty normal here, and I'm an intrigued that it is so hard to get the right info in the BSM; it shouldn't be. -- John _______________________________________________ mlvm-dev mailing list mlvm-dev@openjdk.java.net http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
