JDK-8047818 : G1 HeapRegions can no longer be ContiguousSpaces
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2014-06-23
  • Updated: 2015-01-21
  • Resolved: 2014-06-26
The Version table provides details related to the release that this issue/RFE will be addressed.

Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.

To download the current JDK release, click here.
JDK 8 JDK 9
8u40Fixed 9 b24Fixed
Related Reports
Relates :  
JDK-8047820 - G1 Block offset table does not need to support generic Space classes
Relates :  
JDK-8047821 - G1 Does not use the save_marks functionality as intended
Relates :  
JDK-8047819 - G1 HeapRegionDCTOC does not need to inherit ContiguousSpaceDCTOC
Relates :  
JDK-8048183 - Unify allocation code in ContiguousSpace and G1OffsetTableContigSpace
Relates :  
JDK-8048214 - Linker error when compiling G1SATBCardTableModRefBS after include order changes
Description
When G1 is modified to unload classes without doing full collections the old HeapRegions 
can contain unparseable objects. 
This makes ContiguousSpace unsuitable as a base class for HeapRegion since it assumes that all objects below _top are parseable.

Modify G1OffsetTableContigSpace to implement allocation with a separate _top and reimplement some Space pure virtuals to make object iteration work as expected.