there's some specific tuning JVM configuration for AmazonWS/EC2 building blocks (small, large...)?
Somebody have suggestions for tuning JVM running on these machine profiles?
This is highly application specific, and really has little to do with EC2 specifically. The only difference on EC2 versus a regular server is that performance is not guaranteed--so pick some safe values and load test.
That being said, here are a few links to get you started:
But you'll get much better mileage if you find something specific to your Java application.