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Java 6 and 64bit max memory

 
 
robert
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      12-29-2006
Hi all,

On 32bit JVM's I've never had luck going over 2GB of heap, including
tweaking OS parameters. My current project has a few dual x64 machines
running on XP (not linux unfortunately) . Anyways, our app uses more
memory via the JVM than processor, and the 2GB JVM heap limit is
reached far earlier than the dual x64 processors rise above 50%
capacity.

I noticed Java 6 64bit JVM support for XP x64 - intel. Does anyone know
if for example I have 8GB of memory . I can raise the max heap size to
6GB ? The example assumes nothing else on the machine, just running
jboss / hibernate and uses lots of memory. I'm asking because before I
recommending purchasing more memory, I can use it. I did a lot of
googling but didn't turn up any specifics.

Robert

 
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Patricia Shanahan
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      12-29-2006
robert wrote:
> Hi all,
>
> On 32bit JVM's I've never had luck going over 2GB of heap, including
> tweaking OS parameters. My current project has a few dual x64 machines
> running on XP (not linux unfortunately) . Anyways, our app uses more
> memory via the JVM than processor, and the 2GB JVM heap limit is
> reached far earlier than the dual x64 processors rise above 50%
> capacity.
>
> I noticed Java 6 64bit JVM support for XP x64 - intel. Does anyone know
> if for example I have 8GB of memory . I can raise the max heap size to
> 6GB ? The example assumes nothing else on the machine, just running
> jboss / hibernate and uses lots of memory. I'm asking because before I
> recommending purchasing more memory, I can use it. I did a lot of
> googling but didn't turn up any specifics.
>
> Robert
>


A 64-bit JVM, given sufficient physical memory, does remove the 2 GB
heap limit. I don't know what the effective limit will be for your
configuration.

Maybe, if nobody does know specifically, you could test by borrowing
memory, or getting access to a similar system with more memory?

Patricia
 
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=?ISO-8859-1?Q?Arne_Vajh=F8j?=
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Posts: n/a
 
      12-29-2006
robert wrote:
> On 32bit JVM's I've never had luck going over 2GB of heap, including
> tweaking OS parameters. My current project has a few dual x64 machines
> running on XP (not linux unfortunately) . Anyways, our app uses more
> memory via the JVM than processor, and the 2GB JVM heap limit is
> reached far earlier than the dual x64 processors rise above 50%
> capacity.
>
> I noticed Java 6 64bit JVM support for XP x64 - intel. Does anyone know
> if for example I have 8GB of memory . I can raise the max heap size to
> 6GB ? The example assumes nothing else on the machine, just running
> jboss / hibernate and uses lots of memory. I'm asking because before I
> recommending purchasing more memory, I can use it. I did a lot of
> googling but didn't turn up any specifics.


http://www.theserverside.net/tt/arti...#_Toc104911912

Are running WAS 6.0 with 14.5 GB heap size on both Windows 2003
64 bit and Redhat Linux 64 bit.

That is with IBM JVM.

http://www.spec.org/jbb2005/results/...0815-00179.txt

3.7 GB heap size with JRockit JVM.

>2 GB has been seen.


Arne

 
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Daniel Pitts
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      12-30-2006

robert wrote:
> Hi all,
>
> On 32bit JVM's I've never had luck going over 2GB of heap, including
> tweaking OS parameters. My current project has a few dual x64 machines
> running on XP (not linux unfortunately) . Anyways, our app uses more
> memory via the JVM than processor, and the 2GB JVM heap limit is
> reached far earlier than the dual x64 processors rise above 50%
> capacity.
>
> I noticed Java 6 64bit JVM support for XP x64 - intel. Does anyone know
> if for example I have 8GB of memory . I can raise the max heap size to
> 6GB ? The example assumes nothing else on the machine, just running
> jboss / hibernate and uses lots of memory. I'm asking because before I
> recommending purchasing more memory, I can use it. I did a lot of
> googling but didn't turn up any specifics.
>
> Robert


I might recommend trying to find a way to reduce your memory
requirements. I know its not always possible, but sometimes a tweak in
any algorithms you use might help signifigantly. Using lazy loading in
hibernate might help some, and possibly throttling usage, or
distributing usage via a load-balancer might be useful too.

 
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