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  1. JDK
  2. JDK-8263002

Remove CDS MiscCode region

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    • b13

    Description

      The CDS MiscCode region is used for:
      (a) C++ vtables
      (b) Method trampolines

      (a) can be moved to the ReadWrite region
      (b) were introduced in JDK-8145221 so we can delay writing into Methods. This was intended to improve copy-on-write sharing to reduce memory footprint. However, this hasn't been shown to have any significant effect (footprint of metadata usually is much smaller than the Java heap), and introduces a lot of complexity in the HotSpot code.

      Removing (b) will make it easier to implement JDK-8026297 (Generating AdapterHandlerEntry during CDS dump), which will further improve start-up time.

      ============
      Other benefits of removing the MiscCode region:

      - We no longer have a read/write/executable region. This address the concern in JDK-8262922.
      - We can enable CDS on macOS/AArch64, which does not allow read/write/executable regions. (JDK-8253795)

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          duplicates

          Enhancement - null JDK-8246015 Method::link_method is called twice for CDS methods

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. JDK-8263054 [testbug] SharedArchiveConsistency.java reuses jsa files

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Enhancement - null JDK-8253795 Implementation of JEP 391: macOS/AArch64 Port

          • P2 - Crashes, loss of data, severe memory leak.
          • Resolved

          Enhancement - null JDK-8145221 Use trampolines for i2i and i2c entries in Methods that are stored in CDS archive

          • P3 - Major loss of function.
          • Resolved

          Enhancement - null JDK-8026297 Generate AdapterHandlerEntry during CDS dump

          • P3 - Major loss of function.
          • Open

          Enhancement - null JDK-8262922 Randomise mapped CDS address and relocate pointers by default

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Enhancement - null JDK-8264240 [macos_aarch64] enable appcds support after JDK-8263002

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved
          links to

          Commit Commit openjdk/jdk/d8a9c3ca

          Review Review openjdk/jdk/2861

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              iklam Ioi Lam
              iklam Ioi Lam
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                Created:
                Updated:
                Resolved: