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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: [OT] IIS7/isapi/tomcat performance
Date Thu, 03 Mar 2011 05:51:01 GMT
> From: Tony Anecito [mailto:adanecito@yahoo.com] 
> Subject: Re: [OT] IIS7/isapi/tomcat performance

> On page 4 of the following port guide:
> http://public.dhe.ibm.com/software/dw/jdk/64bitporting/64BitJavaPortingGuide.pdf

> It states:For Windows, on 32-bit systems, integers, longs and 
> pointers are all 32-bits. On 64-bit systems, integers and longs
> remain 32-bits, but pointers become 64-bits and long longs are 
> 64-bits.

That ancient porting guide is misleading in several respects, one in particular being that
the OS determines the size of language-specific types.  That is incorrect; it's the *compiler*
being used that makes that determination, not the platform or the OS.

> This would explain why Windows might seem to run faster than 
> Linux for 64-bit.

Sorry, that's completely false.  As Chris pointed out, Java non-reference type sizes are fixed,
and are completely independent of the platform the Java program is running on.  The only thing
that changes between a 32-bit JVM and a 64-bit one is the size of a reference (pointer). 
Even in the C and C++ code that makes up the core of the JVM, the programmers studiously avoid
use of ambiguous C types such as int and long anywhere that it might make a difference, and
instead use explicitly sized types.

 - Chuck


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