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

Asked 2009-02-18T01:04:16.890
12

We run the 32-bit Sun Java 5 JVM on 64-bit Linux 2.6 servers, but apparently this limits our maximum memory per process to 2GB. So it's been proposed that we upgrade to the 64-bit JVM's to remove the restriction. We currently run multiple JVM's (Tomcat instances) on a server in order to stay under the 2GB limit, but we'd like to consolidate them in the interest of simplifying deployment.

If you've done this, can you share your experiences, please? Are you running 64-bit JVM's in production? Would you recommend staying at Java 5, or would it be ok to move to both Java 6 and 64 bits simultaneously? Should we expect performance issues, either better or worse? Are there any particular areas we should focus our regression testing?

Thanks for any tips!

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2 Answers

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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.

answered 2009-02-18T01:24:18.200
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After migrating to JDK6 64bits from JDK5 32bits (Windows server), we got leak in "perm gen space" memory block. After playing with JDK parameters it was resolved. Hope you will be more lucky then we are.

answered 2009-02-18T17:59:54.390

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