JDK-8210063 : ZGC: Enable load barriers for IN_NATIVE runtime barriers
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2018-08-28
  • Updated: 2021-07-12
  • Resolved: 2018-08-30
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JDK 11 JDK 12
11.0.13-oracleFixed 12 b10Fixed
Related Reports
Blocks :  
JDK-8215451 - JNI IsSameObject should not keep objects alive
Relates :  
JDK-8212992 - Change mirror accessor in Klass::verify_on() to use AS_NO_KEEPALIVE
Description
In an effort to scan more root sets concurrently, we need to support IN_NATIVE oops not being fixed up in safepoints. Both the ZBarrierSetAssembler, ZBarrierSetC1 and ZBarrierSetC2 already have IN_NATIVE load barriers on for all strong oops. However, ZBarrierSet does not yet enable it. I propose to enable it so we can scan more things concurrently.
Comments
Fix Request (11u) This fixes ZGC to accept load barriers on native locations (as ZBSA, ZBSC1, ZBSC2 already do), which opens the way to backport JDK-8215451. Patch applies cleanly to 11u, passes tier1, tier2 tests.
25-06-2019
[~shade] I can't think of a reason why this wouldn't be safe to backport to 11. So... go for it! Thanks for backporting it.
25-06-2019
Looking for 11u backports for Shenandoah, I think this fix is required for JDK-8215451 to work. Otherwise, compiler/gcbarriers/UnsafeIntrinsicsTest.java fails with "unexpected decorator". The change itself looks simple and safe. Erik, can you see any problems with backporting it to 11u?
25-06-2019