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  1. JDK
  2. JDK-8057845

ClassVerifier::verify_exception_handler_targets reconstructs the ExceptionTable in a loop

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    Details

    • Type: Enhancement
    • Status: Closed
    • Priority: P4
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 9
    • Component/s: hotspot
    • Subcomponent:
    • Resolved In Build:
      b34
    • Verification:
      Not verified

      Backports

        Description

        If one runs a classloader benchmark:
          http://cr.openjdk.java.net/~shade/8053904/benchmarks.jar

        ...with Nashorn-generated class files:
         http://cr.openjdk.java.net/~shade/8053904/classes.jar

        ...and jdk9 executed as:
         $ java -jar benchmarks.jar -wi 0 -i 30 -r 10s -p file=classes.jar

        ...one can produce this profile:
         http://cr.openjdk.java.net/~shade/8053904/class-install-calltree-2.txt

        Looking closely at this profile, one can note an interesting thing: ClassVerifier::verify_exception_handler_targets seems to spend a lot of time reconstructing the exception table:
          +- 30.470 (9%) ClassVerifier::verify_exception_handler_targets(unsigned short,bool,StackMapFrame*,StackMapTable*,Thread*)
          | +- 11.350 (3%) ConstMethod::exception_table_length()const
          | +- 11.270 (3%) ConstMethod::exception_table_start()const

        This seems to be an offending piece of code:

          ExceptionTable exhandlers(_method());
          int exlength = exhandlers.length();
          for(int i = 0; i < exlength; i++) {
            //reacquire the table in case a GC happened
            ExceptionTable exhandlers(_method());

        ...and this seems to be the history behind it:
        http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2012-June/003913.html

        I think we need to reconsider the approach of reconstructing the exception table on every loop iteration.

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                Assignee:
                hseigel Harold Seigel
                Reporter:
                shade Aleksey Shipilev
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                  Updated:
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