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  1. JDK
  2. JDK-7148605

Use FS/GS for JVM thread TLS on Ivy Bridge

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    Details

    • Type: Enhancement
    • Status: Closed
    • Priority: P3
    • Resolution: Won't Fix
    • Affects Version/s: hs24
    • Fix Version/s: 9
    • Component/s: hotspot
    • Subcomponent:
    • CPU:
      x86
    • OS:
      generic

      Description

      Ivy Bridge, the 22nm followon from Sandy Bridge, will allow user mode access to FS
      and GS. One or the other of these registers is currently used by the OS to hold
      the address of the operating system's thread-local-storage. If the other isn't
      used by the OS, and can be set in user mode, then it can be used to hold the
      address of the JavaThread structure for a given thread, i.e., the JVM TLS. On
      64-bit, this would free up r15 for general use (it currently contains the JVM
      TLS address), and on 32-bit, it would make possible to eliminate calls to
      pthread_getspecific (posix) or thr_getspecific (solaris), or in the cases where
      OS TLS is directly accessible, eliminate the load(s) required to get the JVM
      TLS address into a register.

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            Assignee:
            Unassigned Unassigned
            Reporter:
            phh Paul Hohensee
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