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  1. JDK
  2. JDK-8292591

Experimentally add back barrier-less Java thread transitions

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Details

    • Enhancement
    • Resolution: Fixed
    • P4
    • 20
    • 20
    • hotspot
    • None
    • b15

    Description

      In some extreme workloads where JNI is used for calling a very, very short function very, very often, there is a very small performance benefit from using the unsupported JNI critical.

      JNI critical does not properly leave the VM when going to native (which can block for safepoints) and gives access to the heap directly in case of a primitive array.

      JNI critical has been removed.

      The primitive array case seems not be well known (good!) and we have not seen any concerns about that.
      But the lack of faster JNI calls has been noted.

      If we only need the faster transitions the best idea for it is to add back barrier-less transitions. It is almost as fast as JNI critical, but applies to all ordinary JNI methods. (JNI critical had simpler argument packing due to blocking safepoints)

      This time we want to:
      - Use documented and supported OS features.
      - Leave it as an experimental feature, and document that it may be removed in any release without prior notice.

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          is blocked by

          Bug - A problem which impairs or prevents the functions of the product. JDK-8292592 JFR test TestNative is not reliable due to low rate of sampling.

          • P5 - Cosmetic problem like misspelt words or misaligned text.
          • Resolved
          relates to

          Bug - A problem which impairs or prevents the functions of the product. JDK-8295666 Linux x86 build fails after 8292591

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8293771 runtime/handshake/SystemMembarHandshakeTransitionTest.java fails if MEMBARRIER_CMD_QUERY is unsupported

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

          Enhancement - null JDK-8303210 [linux, Windows] Make UseSystemMemoryBarrier available as product flag

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

          Bug - A problem which impairs or prevents the functions of the product. JDK-8289302 Restore CriticalJNINatives

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8295395 Linux Alpha Zero builds fail after JDK-8292591

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

          Bug - A problem which impairs or prevents the functions of the product. JDK-8321075 RISC-V: UseSystemMemoryBarrier lacking proper OS support

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

          Bug - A problem which impairs or prevents the functions of the product. JDK-8293787 Linux aarch64 build fails after 8292591

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

          Enhancement - null JDK-8293922 Extend barrier-less Java thread transitions to native transitions

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

          Commit Commit openjdk/jdk/1e1db5de

          Review Review openjdk/jdk/10123

          Activity

            People

              rehn Robbin Ehn
              rehn Robbin Ehn
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              Dates

                Created:
                Updated:
                Resolved: