JDK-7120038 : G1: ParallelGCThreads==0 is broken
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 7u4
  • Priority: P4
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2011-12-09
  • Updated: 2013-09-18
  • Resolved: 2012-01-20
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JDK 7 JDK 8 Other
7u4Fixed 8Fixed hs23Fixed
While testing the changes for 7119908 I ran the GC test suite with -XX:ParallelGCThreads==0 and got several failures - specifically in GCBasher and dacapo2006.

The bulk of these failures were SEGVs due to accessing the FlexibleWorkGang (which does not exist when whne PGCT==0), others were asserts.

There is an RFE to remove the PGCT==0 specific code but until then...

EVALUATION http://hg.openjdk.java.net/lambda/lambda/hotspot/rev/adedfbbf0360

EVALUATION http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/adedfbbf0360

EVALUATION Various SEGVs and asserts when PGCT==0. Most are the result of accessing the worker gang (which is only created when PGCT!=0) outside of a suitable guard.