JVM performance tuning for large applications

Question

The default JVM parameters are not optimal for running large applications. Any insights from people who have tuned it on a real application would be helpful. We are running the

Answer 1

There are great quantities of that information around.

First, profile the code before tuning the JVM.

Second, read the JVM documentation carefully; there are a lot of sort of "urban legends" around. For example, the -server flag only helps if the JVM is staying resident and running for some time; -server "turns up" the JIT/HotSpot, and that needs to have many passes through the same path to get turned up. -server, on the other hand, slows initial execution of the JVM, as there's more setup time.

There are several good books and websites around. See, for example, http://www.javaperformancetuning.com/