Should I use a 32- or a 64-bit JVM?

2012-Nov-23 | Tags: 32or64java

Start64!This is a question I have faced several times during my career in enterprise software development. Every once in awhile I’ve had to hand out recommendations for configuring a specific new environment. And more often than not, part of the question at hand was related to “Should I use a 32- or a 64-bit JVM”. To be honest, in the beginning I just flipped the coin. Instead of giving a reasoned answer. (Sorry, bros!) But by now I have gathered some more insight on this and thought to share it with you.

First stop – the more, the merrier. Right? So – as 64 > 32 then this would be an easy answer: if possible, always choose 64-bit? Well, hold your horses. The downside of the 64-bit architecture is that the same data structures consume more memory. A lot more. Our measurements show that depending on the JVM version and the operating system version along with hardware architecture you end up using 30-50% more heap than on 32-bit. Larger heap can also introduce longer GC pauses affecting application latency – running a full GC on a 4.5GB heap is definitely going to take longer than on a 3GB one. So it will not be correct to jump on the 64-bit bandwagon just because 64 is bigger than 32.

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