JDK-8204951 : Investigate to use WorkGang for Parallel GC
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 11
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2018-06-13
  • Updated: 2021-05-17
  • Resolved: 2019-08-30
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JDK 14
14Fixed
Related Reports
Blocks :  
JDK-8210100 - ParallelGC should use parallel WeakProcessor
Relates :  
JDK-8231670 - Remove TaskExecutor abstraction used in preserved marks processing
Relates :  
JDK-8231672 - Simplify the reference processing parallelization framework
Relates :  
JDK-4996670 - RFE: ParallelScavenge needs NoResourceMarkVerifier guards
Relates :  
JDK-8231669 - Remove WorkerManager abstraction to support multiple work gang implementations
Relates :  
JDK-8267214 - assert(cm->region_stack()->is_empty()) failed: Region stack 0 is not empty
Relates :  
JDK-8224660 - Parallel GC: Use WorkGang (2: MarksFromRootsTask)
Relates :  
JDK-8224659 - Parallel GC: Use WorkGang (1: PCRefProcTask)
Relates :  
JDK-8224662 - Parallel GC: Use WorkGang (4: SharedRestorePreservedMarksTaskExecutor)
Relates :  
JDK-8224663 - Parallel GC: Use WorkGang (5: ScavengeRootsTask)
Relates :  
JDK-8224664 - Parallel GC: Use WorkGang (6: PSRefProcTaskProxy)
Relates :  
JDK-8224665 - Parallel GC: Use WorkGang (7: remove task manager)
Relates :  
JDK-8224666 - Parallel GC: Use WorkGang (8: obsolete and remove flags)
Relates :  
JDK-8204686 - Dynamic parallel reference processing support for Parallel GC
Relates :  
JDK-8224661 - Parallel GC: Use WorkGang (3: UpdateDensePrefixAndCompactionTask)
Description
All collectors but parallel gc use WorkGang to implement parallelism.

This again and again causes us to add an additional abstraction layer above any code that tries to use parallel threads for all collectors (evacuation failure, dynamic thread sizing, reference processing, ...).

Further the parallel gc task queue mechanism has disadvantages:
- the work (tasks) must be known beforehand
- getting work from the task queue incurs taking a global lock which is actually known for being inefficient in literature already

Investigate to replace the parallel gc task queue mechanism with a work gang.

proposed solution:
JDK-8224659
JDK-8224660
JDK-8224661
JDK-8224662
JDK-8224663
JDK-8224664
JDK-8224665
JDK-8224666