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  1. JDK
  2. JDK-8261894 Remove support for UseSHM
  3. JDK-8315498

Release Note: The Linux Specific Options `UseSHM` and `UseHugeTLBFS` Are Now Obsolete

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    • Sub-task
    • Resolution: Delivered
    • P4
    • 22
    • 22
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    Description

      On Linux, if `UseLargePages` is enabled and `UseTransparentHugePages` is disabled, *static* or *explicit* large page mode, the options `UseSHM` and `UseHugeTLBFS` existed to switch between the two different implementations:

      - `UseHugeTLBFS` would cause the JVM to use POSIX APIs for allocating large pages.
      - `UseSHM` would let the JVM would use System V APIs. `UseHugeTLBFS` had been the default if both options were omitted.

      The `UseSHM` mode offered no advantage over `UseHugeTLBFS` and has therefore been removed. The switch `UseSHM` has been obsoleted.

      The JVM will now always use POSIX APIs for managing large pages. The switch `UseHugeTLBFS` has also been obsoleted; `UseHugeTLBFS` is now unconditionally enabled and cannot be switched off.

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            stuefe Thomas Stuefe
            stuefe Thomas Stuefe
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