Temp memory needed for CMS heap compaction?

Discussion in 'Java' started by Kevin McMurtrie, Apr 26, 2008.

  1. Does anyone have inside information on how much temporary memory Sun
    Java 1.5 needs for heap compaction while using the CMS collector? I'm
    tuning new 16GB 64 bit Solaris systems where the Java heap is mostly
    small objects. If I shrink the Java heap too much, there's physical
    memory sitting idle for all but that one moment in a day when it
    compacts. If I make the Java heap too large, it will swap so badly on
    compaction that the server will be marked as down. So far I have an
    estimate that the temp memory for compaction is 50% of the Java heap
    size. Is there a better estimate? I'm not seeing this in Sun's tuning
    guides.

    --
    Block Google's spam and enjoy Usenet again.
    Reply with Google and I won't hear from you.
     
    Kevin McMurtrie, Apr 26, 2008
    #1
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  2. Kevin McMurtrie

    Roedy Green Guest

    On Fri, 25 Apr 2008 20:46:47 -0700, Kevin McMurtrie
    <> wrote, quoted or indirectly quoted someone
    who said :

    >If I shrink the Java heap too much, there's physical
    >memory sitting idle for all but that one moment in a day when it
    >compacts.


    There are so many factors, I think the only way to solve this is to do
    a binary search to home in on the best value.

    See http://mindprod.com/project/tweakable.html

    Unfortunately, that best value will change as soon as you process a
    bigger data set, or you run something else at the same time.
    --

    Roedy Green Canadian Mind Products
    The Java Glossary
    http://mindprod.com
     
    Roedy Green, Apr 26, 2008
    #2
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