Benefits/drawbacks to running 64-bit JVM on 64-bit Linux server?

At the Kepler Science Operations Center we have about 50 machines with 32-64G each. The JVMs heaps are typically 7-20G. We are using Java 6. The OS has Linux 2.6 kernel.

When we migrated to 64bit I expected there would be some issues with running the 64-bit JVM But really there have not been. Out of memory conditions are more difficult to debug since the heap dumps are so much larger. The Java Service Wrapper needed some modifications to support larger heap sizes.

There are some sites on the web claiming GC does not scale well past 2G, but I've not seen any problems. Finally, we are doing throughput intensive rather interactive intensive computing. I've never looked at latency differences; my guess is worst case GC latency will be longer with the larger heap sizes.

We use a 64-bit JVM with heaps of around 40 Gb. In our application, a lot of data is cached, resulting in a large "old" generation. The default garbage collection settings did not work well and needed some painful tuning in production. Lesson: make sure that you have adequate load-testing infrastructure before you scale up like this. That said, once we got the kinks worked out, GC performance has been great.

I can confirm Sean's experience. We are running pure-Java, computationally intensive web services (home-cooked Jetty integration, with nowadays more than 1k servlet threads, and >6Gb of loaded data in memory), and all our applications scaled very well to a 64 bit JVM when we migrated 2 years ago. I would advise to use the latest Sun JVM, as substantial improvement in the GC overhead have been done in the last few releases. I did not have any issue with Tanukisoftware's Wrapper either.