Hello, fellow implementer :-) On Mon, Aug 18, 2014 at 6:01 AM, Raffaello Giulietti <raffaello.giulie...@gmail.com> wrote: > So, the question is whether some of you has experience with large scale > projects written in a dynamic language implemented on the JVM, that makes > heavy use of indy and PICs. I'm curious about the memory load for the PICs. > I'm also interested whether the standard Oracle server JVM satisfactorily > keeps up with the load.
JRuby has implemented call sites using this sort of PIC structure since the beginning. I dare say we were the first. Experimentally, I determined that the cost of a PIC became greater than a non-indy, non-inlining monomorphic cache at about 5 deep. By cost, I mean the overhead involved in dispatching fromthe caller to an empty method....essentially just the cost of the plumbing. Now of course that number's going to vary, but overall a small PIC seems to have value...especially when you consider that the cost of rebinding a call site is rather high. We do have JRuby users using our indy logic in production, and none of their concerns have had any relation to the PIC (usually, it's just startup/warmup concerns). > For example, we have a large Smalltalk application with about 50'000 classes > and about 600'000 methods. In Smalltalk, almost everything in code is a > method invocation, including operators like +, <=, etc. I estimate some 5-10 > millions method invocation sites. How many of them are active during a > typical execution, I couldn't tell. But if the Smalltalk runtime were > implemented on the JVM, PICs would quite certainly represent a formidable > share of the memory footprint. That's why you limit their size. If an inline cache behind a GWT takes up N bytes in memory, a PIC based on the same invalidation logic should just be N * X where X is the depth of your PIC. Of course, you could do what we do in JRuby, and make the PIC depth configurable to try out a few things. > More generally, apart from toy examples, are there studies in real-world > usage of indy and PICs in large applications? > Perhaps some figures from the JRuby folks, or better, their users' > applications would be interesting. The only "studies" we have are the handful of JRuby users running with indy enabled in production. They love the higher performance, hate the startup/warmup time, and most of them had to either bump permgen up or switch to Java 8 to handle the extra code generation happening in indy. I'm happy to answer any other questions. - Charlie _______________________________________________ mlvm-dev mailing list mlvm-dev@openjdk.java.net http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
