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  1. JDK
  2. JDK-6916623

Align object to 16 bytes to use Compressed Oops with java heap up to 64Gb

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    Details

    • Type: Enhancement
    • Status: Closed
    • Priority: P5
    • Resolution: Fixed
    • Affects Version/s: hs17
    • Fix Version/s: hs19
    • Component/s: hotspot
    • Labels:
    • Subcomponent:
    • Resolved In Build:
      b03
    • CPU:
      sparc
    • OS:
      solaris_10
    • Verification:
      Verified

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        Description

        Whenever we decide to use Compressed Oops with 64Gb heap AT LEAST next changes should be made to build VM which support it.
        Note: more complex changes needed to use a VM option. I don't see benefits on N2 with it so I am putting it on shelf.

        src/share/vm/utilities/globalDefinitions.hpp
        @@ -288,11 +288,11
         // Minimum is max(BytesPerLong, BytesPerDouble, BytesPerOop) / HeapWordSize, so jlong, jdouble and
         // reference fields can be naturally aligned.
         
        -const int MinObjAlignment = HeapWordsPerLong;
        +const int MinObjAlignment = HeapWordsPerLong * 2; // *2 for 16 bytes alignment
         const int MinObjAlignmentInBytes = MinObjAlignment * HeapWordSize;
         const int MinObjAlignmentInBytesMask = MinObjAlignmentInBytes - 1;
         
        -const int LogMinObjAlignment = LogHeapWordsPerLong;
        +const int LogMinObjAlignment = LogHeapWordsPerLong + 1; // +1 for 16 bytes alignment
         const int LogMinObjAlignmentInBytes = LogMinObjAlignment + LogHeapWordSize;

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                Assignee:
                kvn Vladimir Kozlov
                Reporter:
                kvn Vladimir Kozlov
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