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Possible Duplicate:
Benefits of 64bit Java platform

All of our client sites are running on 32bit Virtual machines and we're debating whether or not to switch all of them to 64bit VMs.

Is there any advantage(Other than the obvious memory uziliation) to switching to the 64bit VM?

Community
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Tim Sparg
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Main advantages:

  • 64-bit VMs can use more registers and new instructions in the 64-bit instruction set which can improve performance of JIT-compiled code
  • You are no longer limited to 32-bit heap sizes (this is unlikely to be a problem in normal usage, but could make a difference in some special cases e.g. if you are processing very large data arrays)

Main disadvantages:

  • 64-bit pointers take up more space, so your code and data will require marginally more memory. Might be a minor issue if you are memory/cache constrained.

In my experience, both 32-bit and 64-bit VMs have both worked perfectly fine. So unless you are having a measurable problem with one or the other, there isn't much compelling reason to switch at present. For new deployments, I'd probably go for 64-bit VMs.

mikera
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    +1: If you use `-XX:+UseCompressedOops` on the Sun/Oracle 64-bit JVM it will use 32-bit references, using the same amount of memory as the 32-bit JVM. (It can still address 32 GB ;) – Peter Lawrey Jun 03 '11 at 10:24