According to an article Groovy has
Unfortunately at the same time Groovy is very slow at runtime. As a person, who did a lot to improve performance of Groovy I can probably speak about that very openly. Groovy is very slow. You can easily expect that some Groovy calculation or data transformation rewritten in Java will become 3-5 times faster. Usually this factor is 8-12 and sometimes even higher. Someone can say that Java is always at our service and nobody uses Groovy for calculations or data processing... But, hey, it is exactly my point - why should we limit ourselves for just scripting or handling of simple web pages?
What is even worse is the fact that Groovy doesn't scale well for multi-core computers meaning that several threads executing code compiled by Groovy really prevent each other from being fast. It is not a problem for many applications but for many others it is simply show-stopper.
Could someone proof or refute that paragraphs?
I am particularly concerned about multi threading performance.