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  1. JDK
  2. JDK-6446958

Method compilation stops firing of hotspot:::object-alloc probes for one dimensional array allocs.

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P2
    • Resolution: Fixed
    • Affects Version/s: 6
    • Fix Version/s: 6
    • Component/s: hotspot
    • Subcomponent:
    • Resolved In Build:
      b92
    • CPU:
      generic
    • OS:
      solaris_10
    • Verification:
      Verified

      Description

      hotspot:::object-alloc are not fired for one dimensional array allocations after
      method is get compiled.

      VM flavors : client | server
      VM Modes : -Xmixed | -Xcomp

      It does not work for both primitive types and objects.
      However, it does work for for multidimensional array allocations.

      Here is the result of running with -Xcomp:
      # java -XX:+UnlockDiagnosticVMOptions -XX:+PauseAtStartup -XX:+ExtendedDTraceProbes -Xcomp Main & JAVA_PID=$!
      # ./alloc.d vm.paused.$JAVA_PID -p $JAVA_PID
          method calls: 366 allocMultiDimIntArrayOf
          method calls: 366 allocOneDimIntArrayOf
          object allocs: 366 [[I

          method calls: 864 allocMultiDimIntArrayOf
          method calls: 864 allocOneDimIntArrayOf
          object allocs: 864 [[I

      No probes are fired for "[I" at all.

      Here is the result of running with -Xmixed:
      # java -XX:+UnlockDiagnosticVMOptions -XX:+PauseAtStartup -XX:+ExtendedDTraceProbes -Xmixed -XX:CompileThreshold=100 Main & JAVA_PID=$!
      # ./alloc.d vm.paused.$JAVA_PID -p $JAVA_PID
          method calls: 394 allocMultiDimIntArrayOf
          method calls: 394 allocOneDimIntArrayOf
          object allocs: 101 [I
          object allocs: 395 [[I

          method calls: 894 allocMultiDimIntArrayOf
          method calls: 894 allocOneDimIntArrayOf
          object allocs: 101 [I
          object allocs: 895 [[I

      Probes were fired only for first 101 allocations
      (before allocOneDimIntArrayOf was compiled).

      The observation from Sundar:
      It is probably related to different instructions used to allocate arrays -
      for one dimensional arrays "anewarray/newarray" is used
      and for multidimensional arrays - "multianewarray".

      Steps to reproduce (files are attached):
      1. javac Main.java
      2. java -Xcomp -XX:+UnlockDiagnosticVMOptions -XX:+PauseAtStartup -XX:+ExtendedDTraceProbes Main & JAVA_PID=$!
      3. ./alloc.d vm.paused.$JAVA_PID -p $JAVA_PID

      Thanks Amit for finding this issue.

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            Assignee:
            never Tom Rodriguez
            Reporter:
            epavlova Ekaterina Pavlova
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