This is a Tomcat forum so lets focus on the role of memory in a Servlet
Engine.
Read the Microsoft paper.
http://msdn2.microsoft.com/en-us/vstudio/aa700838.aspx
Bigger memory space means better performance when you have large
numbers of users.
If you are designing a Tomcat application for a hundred users, you can
take whatever you want (or can find) for hardware.
If you are hoping to handle thousands of users, you will be a lot better
off on 64 bits.
The faster arithmetic of 64 bits is not as important as the ability to
use more than 2Gb (Windows) or 4GB (Linux) of memory for your Tomcat
application and cache, transaction buffers, etc.
Here is IBM's view on how Linux works in a 32 bit environment. You can
see the gyrations that have to be done to arrange processes in a 32 bit
world.
http://www.ibm.com/developerworks/linux/library/l-memmod/
From a strategic point of view, 64 bit is clearly the way of the future
and each new version of the OS, Java VM and all of the supporting
libraries will have more optimization for 64 bit memory management and
arithmetic.
The leaders in Web technology have already moved to 64 bits, the rest of
us will follow.
It is not clear that you can even purchase a server from the major
vendors that does not have a 64 bit processor. I did not see any 32 bit
servers at HP.
If 64 bit was not a competitive advantage this would not happen.
Ron
Andrew Miehs wrote:
On 29/07/2007, at 2:34 PM, Peter Stavrinides wrote:
32 bits processors can represent numbers up to 4,294,967,295 while a
64-bit machine can represent numbers up to
18,446,744,073,709,551,615. For modern hardware to take advantage of
the processing power of the 64 bit architecture a system must have a
minimum 4GB Ram, but probably needs significantly more and more
importantly the CAPACITY to take full advantage of it, allocating it
to running processes, with less there is potential for lag.
64bit machines have been around since the 60's but only now are
software and hardware vendors supporting it for the mainstream
market. So is 64bit better than 32bit right now? the answer is yes, a
64-bit processor has more technology, a better design with more
transistors, thus faster speeds are possible. This is currently where
the true benefit of switching to a 64-bit processor lays, it has
nothing to do with the memory address space, which is exactly that,
just space for more complex computations.
This is definitely not looking at the big picture.
Whether or not to go 64bit depends on your application.
BASED ON MY TESTS....
If your application runs in Java AND you are using Sun JVM 1.5 AND
performance is an issue, then I would definitely go 64bit linux.
else if your Java application doesn't have a performance requirement,
but needs lots of memory, be that for caching or anything else, then
I would use 64 bit - Pick your own operating system...
else if the machine you are using has more than 4GB RAM, I would look
at using a 64bit OS, - up to you whether you want 32bit or 64bit Java.
else if none of this applies to you, I would probably run a 32 bit OS,
and wait for someone to port the last remaining packages/ drivers.
BTW More transistors mean less CPU clock speed - not more... (But I
think you meant larger operations per cycle).
Cheers
Andrew
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