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Re: 64 bit Java on Mac OS/X
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Re: 64 bit Java on Mac OS/X




On Dec 14, 2006, at 5:31 AM, Van Simmons wrote:

I've been trying to find out the details on using Java in 64 bit mode in Mac OS/X. Is this possible under Java 5? If not is it going to be possible in Java 6? I suppose what I'm really trying to find out is if it is possible to heap sizes > 2GB.

Java on Mac OS X depends on frameworks and libraries that don't provide 64-bit interfaces on 10.4 or earlier however Mac OS X 10.5 is expanding 64-bit support to all non-deprecated frameworks and application development environments.


The near two 2 GiB limit you currently see for Java isn't a direct limit of a 32-bit virtual address space (32-bit yields 4 GiB address space per process) but is a result of fragmentation of the 32-bit virtual address space. The fragmentation comes about from reserved memory ranges and shared library/framework mappings. If the Java heap was allocated in smaller chunks and not in a large block likely it could grow to near 3.5 GiB in size (about the maximum amount of memory available after you subtract out all of the reserved ranges and mappings).

When dealing with a 64-bit virtual address space the reserved ranges and mapping will reasonably be a non issue given the immense size of a 64-bit virtual address space.

-Shawn

p.s. It isn't called "Mac OS/X" but "Mac OS X".
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 >64 bit Java on Mac OS/X (From: "Van Simmons" <email@hidden>)



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