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From "Leon Rosenberg" <rosenberg.l...@googlemail.com>
Subject Re: Tomcat with 8 GB memory
Date Fri, 27 Jul 2007 22:18:21 GMT
On 7/27/07, Joe Nathan <jowen4077@yahoo.com> wrote:
>
>
> Leon Rosenberg-3 wrote:
> >
> > Could you provide some additional information?
> > So far 64bit machines always outperformed 32bit machines in my
> > personal benchmarks as well as in third party benchmarks I stumbled
> > upon.
> >
> > So it would be great if you could provide some links or explanations.
> >
> > thank you
> > leon
> >
>
> It's for the very simple reason: 64bit machines have 64bit address!
> What is address! It's pointers if you are familiar with C, Pointers
> are 64bit integers. Pointer arithmetics will deal with 64bit addressed
> data. Arithmetic operations on 64bit takes app. twice long as 32bits.

Sorry, this just sounds plain wrong. If a 64 bit processor comes with
64 bit register it means that it can make an integer 64 bit addition
(long) in one operation, which is at least twice as fast as the same
operation on a 32 bit processor, and an addition of a 32 bit integer
is as fast as on a 32 bit processor, at least what you see outside of
the processor.

Further, following your argumentation, 16 bit processor is faster than
32 bit processor and 8 bit faster than 16... hell my abacus rocks.

I admit that my last course in processors is like 10 years ago, but we
actually measured the performance of the same application under 64 bit
java on a 64 bit system and 32 bit java on a 32 bit system, and guess
what, the 64 bit version outperformed the 32 bit version by nearly
10%.

Despite empirical data, the simply marketing logic tells us, that 64
bit processors are faster, at least amd and intel. The 64 bit
processors (as they were introduced) were higher priced as the 32 bit
alternatives and were shipped with larger cache and higher tacts. But
the whole discussion is pointless anyway, since there are no
comparable 32 bit processors on market anymore, and would you agree
that a 64 bit application runs faster on a 64 bit processor than a 32
bit application?


> As this is used very many in compiled binaries pointer arithmetics,
> you should expect 64bit machines will give you slower performance,
> for cpu bound applications. Note that hardware clocking time also
> slower than 32 machines.
>
> However, if your application is "data intensive" (with heaps of data
> caches),
> larger memory can boost quite a lot. You may even get several time
> or more better through put than otherwise. That's why there is a push
> for 64 bit machine.
>
> Also there is another aspect of programming skills. Many servlet programmers
> don't understand underlying garbage collection algorithms. They tend to
> make use lot more memory. If you control memory use smartly,
> this can boost performance significantly as well!

Errm.... WHAT???



regards
Leon

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