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From Peter Stavrinides <p.stavrini...@albourne.com>
Subject Re: Tomcat with 8 GB memory
Date Mon, 30 Jul 2007 06:00:29 GMT
This is really not true, (unless the machine in question is more than 
four years then performance is faster for some operations and slower for 
others), with a new machine you will gain.

Mohan2005 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??
>
> 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 
>>
>> If you are not an intended recipient of this e-mail, please notify the
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>>
>>
>>
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>>
>>
>>     
>
>   

-- 
Peter Stavrinides
Albourne Partners (Cyprus) Ltd
Tel: +357 22 750652 

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