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9 Replies Latest reply: Dec 3, 2012 4:17 PM by 689677 RSS

Maximum Memory Allocation

689677 Newbie
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Hi,
I am having hard time in finding any details on how much is the maximum memory can be allocated to the JVM in JDK 1.6
I vaguely remember the number of cores and 64 or 32 bit architecture are the factors based on which the maximum memory can be decided.

Can you please assist in any such material that can help in finding this out.

Thank you.
  • 1. Re: Maximum Memory Allocation
    Kayaman Guru
    Currently Being Moderated
    32-bit architecture limits the memory to 2G or so.
    There is no limit on 64-bit architecture.
  • 2. Re: Maximum Memory Allocation
    gimbal2 Guru
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    Kayaman wrote:
    There is no limit on 64-bit architecture.
    Sure there is. Just not one you're going to break right now :)
  • 3. Re: Maximum Memory Allocation
    jschellSomeoneStoleMyAlias Expert
    Currently Being Moderated
    Prashant Ladha wrote:
    Hi,
    I am having hard time in finding any details on how much is the maximum memory can be allocated to the JVM in JDK 1.6
    I vaguely remember the number of cores and 64 or 32 bit architecture are the factors based on which the maximum memory can be decided.

    Can you please assist in any such material that can help in finding this out.
    Perhaps what you are referring to is the maximum default heap value that is used when a maximum is not explicitly specified.

    If so it is here.

    http://docs.oracle.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html
  • 4. Re: Maximum Memory Allocation
    689677 Newbie
    Currently Being Moderated
    I am looking for the maximum value that I can specify in Xmx JVM argument with JDK 1.6.
    I understand the maximum value for Xmx is dependent on the number of cores of your server and the Hardware/ OS architecture if it is 64 or 32 bit.
  • 5. Re: Maximum Memory Allocation
    jtahlborn Expert
    Currently Being Moderated
    Prashant Ladha wrote:
    I am looking for the maximum value that I can specify in Xmx JVM argument with JDK 1.6.
    I understand the maximum value for Xmx is dependent on the number of cores of your server and the Hardware/ OS architecture if it is 64 or 32 bit.
    nope. completely unrelated to cores.
  • 6. Re: Maximum Memory Allocation
    689677 Newbie
    Currently Being Moderated
    Thank you for correcting me.
    What is the maximum value that I can specify in the Xmx parameter?

    Edited by: Prashant Ladha on Dec 2, 2012 12:54 PM
  • 7. Re: Maximum Memory Allocation
    Kayaman Guru
    Currently Being Moderated
    Prashant Ladha wrote:
    What is the maximum value that I can specify in the Xmx parameter?
    Try it out.
  • 8. Re: Maximum Memory Allocation
    EJP Guru
    Currently Being Moderated
    What is the maximum value that I can specify in the Xmx parameter?
    1. It is architecture-dependent, as you noted yourself earlier. So there is no single answer.

    2. It is specified in the Garbage Collector Ergonomics document linked earlier, a few lines from the top. Clearly you have clearly not even bothered to look at it.
  • 9. Re: Maximum Memory Allocation
    689677 Newbie
    Currently Being Moderated
    For Point 1, assuming that there are only 2 architectures i.e. 32 or 64 bit, so we will have only 2 answers.
    For Point 2, I did go through the article that was posted above. When the article says "Smaller of 1/4th of the physical memory or 1GB." in the maximum heap section, I know for sure, something is wrong.
    After going through the article over and over again, we realized that the section is named wrong. It should be "default maximum heap size".

    Not to take a dig at what you said, but Clearly, you have clearly not even bothered to understand the header and the matter under it before pointing it to someone.

    Do correct me anywhere you feel right.

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