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From "Leon Rosenberg" <rosenberg.l...@googlemail.com>
Subject Re: Tomcat with 8 GB memory
Date Sun, 29 Jul 2007 19:29:43 GMT
On 7/29/07, Mohan2005 <mohan@roomsnet.com> wrote:
>
> Hello:
>
> we also wish to convert out 32bit dual cores to 64bit dual cores to run java
> applications (multiple instances with large JVM memory)
> but people advice that 64bit are 20 - 30% slower than the 32bit with smaller
> JVM.
> why? and if true how to overcome??
>

dont listen to that people they are talking bullshit :-)
Leon

> thanks
>
>
>
> Peter Stavrinides wrote:
> >
> > Some of arguments presented hold some truths, but look at the bigger
> > picture... the point is that 64bit is a superior architecture to 32 bit,
> > but it is still maturing... the reasons for this are both hardware and
> > software related... the way we write programs will have to change to
> > take advantage of the new architecture, and the current generation of
> > hardware will no doubt mature to realize the potential of 64bit
> > architecture.
> >
> > 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.
> >
> > Peter
> >
> >
> > Alexey Solofnenko wrote:
> >> No, each of two 4GB processes will have only a half of the objects
> >> under the same load. And I heard that GC does not scale linear with
> >> heap size. And this is without multi-threading performance
> >> considerations.  As usual, your mileage may vary and only tests can
> >> tell for sure.
> >>
> >> - Alexey.
> >>
> >> Caldarale, Charles R wrote:
> >>>> From: Alexey Solofnenko [mailto:A.Solofnenko@mdl.com] Subject: Re:
> >>>> Tomcat with 8 GB memory
> >>>>
> >>>> I was under impression that GC does not scale linearly. That means
> >>>> one 8GB process will be slower than two 4GB processes.
> >>>>
> >>>
> >>> Not true.  The time of a full GC using modern algorithms depends mostly
> >>> on the number and type of live objects, not the amount of heap space.
> >>> The number and type of live (reachable) objects stays relatively
> >>> constant for most application once the ramp-up period is over.
> >>> Consequently, running a single JVM with the largest heap you can fit in
> >>> the process space is the most efficient from a GC point of view.  (Of
> >>> course, there are plenty of other reasons not to put all your eggs in
> >>> one basket.)
> >>>
> >>>  - Chuck
> >>>
> >>>
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> >>
> >
> > --
> > Peter Stavrinides
> > Albourne Partners (Cyprus) Ltd
> > Tel: +357 22 750652
> >
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