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  1. JDK
  2. JDK-8182487

Add Unsafe.objectFieldOffset(Class, String)

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    Details

    • Type: Enhancement
    • Status: Resolved
    • Priority: P4
    • Resolution: Fixed
    • Affects Version/s: 10
    • Fix Version/s: 10
    • Component/s: core-libs
    • Resolved In Build:
      b21

      Description

      Core libraries have a number of usages of Unsafe.objectFieldOffset(Field) happen during startup, which means we spend some time loading ReflectionData for these classes.

      I've explored adding a Unsafe.objectFieldOffset(Class, String) instead, and can validate that this approach has small, but measurable benefits to startup and total allocations:

      http://cr.openjdk.java.net/~redestad/scratch/unsafe.offset.jdk
      http://cr.openjdk.java.net/~redestad/scratch/unsafe.offset.hotspot

      - Drops 9 classes from loading altogether on minimal startup tests
      - Drops total instructions spent during startup by around 1.5-2.5M (0.5-1.5ms), scaling depending on how many of the changed classes are loaded (the speedup from not loading 9 classes is only a small part of this).

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            Assignee:
            redestad Claes Redestad
            Reporter:
            redestad Claes Redestad
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