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  1. JDK
  2. JDK-8152083

Optimize TimeUnit conversions

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    • Bug
    • Resolution: Fixed
    • P4
    • 9
    • None
    • core-libs
    • None

    Description

      It's a performance bug, java.util.concurrent.TimeUnit is used when initializing the VM and because it use the abstract enum pattern, it requires to initialize a bunch of anonymous classes.

      java -verbose:class -version
      ...
      [Loaded java.util.concurrent.TimeUnit from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$1 from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$2 from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$3 from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$4 from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$5 from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$6 from jrt:/java.base]
      [Loaded java.util.concurrent.TimeUnit$7 from jrt:/java.base]

      The code of TimeUnit should use a switches (like in toChronoUnit()) instead of relying on virtual dispatch.

      Note that it's perhaps less 'object oriented' to use a switch instead of a virtual dispatch, but given that multiple enum values will be used as argument of a method call like Condition.await, currently the code creates megamorphic callsite inside await() when the enum value is converted to milisecond.

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            martin Martin Buchholz
            forax RĂ©mi Forax
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              Created:
              Updated:
              Resolved: