performance - How to speed up Java VM (JVM) startup time?

Question

I am running tests that start multiple JVM processes. Summary startup time of JVMs is quite significant compared to time of actual tests that run inside JVM. How do I speed things up?

I have used "-client" option already, this does help but not as much as I wanted. Is there any other way, say preloading bunch of JVMs and reusing them somehow?

Answer 1

If you do want to reuse JVMs, the "somehow" could be Nailgun. Nailgun keeps a JVM running, then uses a light native client to start a particular class and handle console io. This is good for running small command line Java utilities, but as it reuses the same JVM can accumulate state.

To work around the state accumulation, at the cost of running multiple JVMs, another option is Drip. Drip keeps a fresh JVM spun up in reserve with the correct classpath and other JVM options so you can quickly connect and use it when needed, then throw it away. Drip hashes the JVM options and stores information about how to connect to the JVM in a directory with the hash value as its name.