Progress! I am staring right now at my JVM 7 build of Clojure that uses invokedynamic for Vars that contain functions. It essentially works, well enough for experimentation. A few of my simple apps seem to work fine with it.
There are still a lot of problems: the Clojure test suite fails, and my re-linking fallback mechanism (based on SwitchPoint) does not differentiate between root bindings of Var and their "box" thread-binding, so in theory any rebinding will cause all linkages on that Var to reset. Not very optimal. I've really done very little optimizing at all at this point: invokedynamic is just replacing the usual invokeinterface. So, I was surprised that when fooling around with some benchmarks, one of them showed about 30% performance improvement on one of my Clojure-built web servers. Tantalizing! But, until the test suite succeeds, I can't be sure that this isn't a side effect of something not so great that's going on. I'm hoping to have something the rest of you can play with soon, but thought you would want to hear a progress report. What would be the most convenient way to share this? A dump to github of the whole tree? A patch? I've used the Clojure 1.2.1 codebase, because I didn't want to work on a moving target, and also think it might be easier for the community to help test this with existing applications. (As I said earlier, I also have a few ideas on how to make sure we can have this mechanism gracefully downgrade to JVM <7.) Many thanks to Paul Stadig and Charlie Nutter for prodding me to realize that the one point where invokedynamic can help is to bridge the gap between dereferencing the Var and then calling invokeinterface on it. My mistake when looking at this the first time around was assuming that the dereferencing and subsequent invokeinterface were fast operations, and that it would make little difference to replace them with invokedynamic. But, speed is not the issue here: it's that this gap represents a black hole for HotSpot, around which it can't optimize well. Because this mechanism represents the primary junction for all of Clojure, optimization here could enable some nifty optimization across the board. I think it's a good way to imagine invokedynamic's benefits: it's a bridge over troubled water for HotSpot. Paul also points out areas where MethodHandles can replace the rather sticky reflection work that Clojure does now to massage calls to non-Clojure libraries. That's not entirely related to the invokedynamic stuff I'm working on, so I think I'll leave it to somebody else to take a stab at that... -Tal -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
