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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: [OT] IIS7/isapi/tomcat performance
Date Thu, 03 Mar 2011 02:12:43 GMT
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Tony,

On 3/1/2011 6:27 PM, Tony Anecito wrote:
> I believe the effect of compression is relative. In other words for a big 
> program with lots of 64-bit pointers and 64-bit longs it is helps but for small 
> programs it does not.

A long in Java is always 64 bits. Those /will/ be faster on a 64-bit
architecture. The only reason any of this is a problem is because
pointers (somewhat) unexpectedly double in size when moving from a
32-bit to a 64-bit platform. If you were running fine in a 128MiB heap
on a 32-bit machine, you may well have to increase your heap size on a
64-bit machine just to store the exact same set of objects.

> I would hope the full 64-bit data bus would be used. So you think 32-pins on the 
> processor are not used when running a 32-bit process?

It depends upon exactly what the processor id doing. Those chips with
bundled x86 cores will use the x86 core (which is /only/ 32-bit, so
there's no option for 64-bit operations). Those chips which have only
x86-64 chips will either use 64 bits to manipulate 32-bit data (and
effectively "waste" the 32 most significant bits) or wave their hands
wildly and achieve some sort of miracle where 32-bit processes run twice
as fast because of a wider word size.

- -chris
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