Java 6 and 64bit max memory

Discussion in 'Java' started by robert, Dec 29, 2006.

  1. robert

    robert Guest

    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
     
    robert, Dec 29, 2006
    #1
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  2. 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
     
    Patricia Shanahan, Dec 29, 2006
    #2
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  3. 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/articles/showarticle.tss?id=NET2BMNov64Bit#_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/res2006q3/jbb2005-20060815-00179.txt

    3.7 GB heap size with JRockit JVM.

    >2 GB has been seen.


    Arne
     
    =?ISO-8859-1?Q?Arne_Vajh=F8j?=, Dec 29, 2006
    #3
  4. robert

    Daniel Pitts Guest

    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.
     
    Daniel Pitts, Dec 30, 2006
    #4
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