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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: max heap size on Windows server 64 bit
Date Mon, 08 Feb 2010 17:24:33 GMT
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Domenico,

On 2/8/2010 11:31 AM, Domenico Marzilli wrote:
> Yes, Chris,
> it depends on the type of data.
> For example:
> 1) the elements of an array are addressed with 64 bit pointers;

Yes, but the array itself does not take up more space, unless it's full
of pointers :)

> 2) on a x32 a long (32bit) is as large as a x64;

I would imagine that a 32-bit long is 32-bits no matter what
architecture it's on. If you mean "what a C compiler will give you if
you use 'long int'", then it depends upon the compiler. Most compilers
use "standard word length" for "long int" (and sometimes int, too) but
it's not part of the C specification.

The Java Language Specification requires 'int' to be a 32-bit number
while a long is defined to be 64-bits, regardless of the architecture.

> By the way, what options for the JVM are you speaking about?

Specifically, -XX:+UseCompressedOOPS

http://java.sun.com/javase/7/docs/technotes/guides/vm/compressedOops.html
http://wikis.sun.com/display/HotSpotInternals/CompressedOops
http://confluence.atlassian.com/display/DOC/Garbage+Collector+Performance+Issues#GarbageCollectorPerformanceIssues-Ifusing64bitJREforlargerheaps%2CuseCompressedOops

- -chris
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