CopyForwardHybrid

[LinHu2016]

CopyForwardHybrid is hybrid mode of CopyForward Scheme that
GC can run both copyforward and markcompact on the collection set
simultaneously (for balanced PGC only). During precollection,
GC can reserve some regions for markcompact only(non evacuated
regions -- such as jni critical regions) and copyforward for
the rest of collection set. CopyForwardHybrid intent to avoid
markcompact PGC due to nonEvacuated regions in collection set,
in order to minimize the longer gc pause time and affection to
concurrent gc.

• new java Option -XXgc:tarokEnableCopyForwardMarkCompactHybrid for
  enabling
  CopyForwardHybrid mode, default is disabled.
• new java Option
  -XXgc:fvtest_forceCopyForwardMarkCompactHybridRatio=nn,
  (1 <=nn<= 100) nn is the percentage of collection set to be reserved
  for markcompact(for margin testing CopyForwardHybrid).
• report copyforward is running hybrid mode in verbose gc
• allow jni critical eden regions in nursery collectionSet for
  copyforward
• _noEvacuation flag in HeapRegionDescriptorVLHGC, set it true
  if the regions can not be evacuated. decide which region can not
  be evacuated in preProcessRegions.
• pull scan work from both scanCache and workPacket in CompleteScan
• synchronize working threads with both scanCache and workPacket
• if live object in non evacurated regions mark map instead of
  copyforward.
• exception case 1: if abort case happens, stop to pull scan work
  from workPacket
• exception case 2: if workPacket overflow during CompleteScan
  set it to abort case to handle overflow

Signed-off-by: Lin Hu [email protected]

[LinHu2016]

This is related pull request #2855 (#2855),
pull request #2855 has been reverted due to failures when running with debug -XXgc:tarokEnableExpensiveAssertions option.
the failures caused by the debugging code, which tries to verify that the references in the Objects inside survivor regions are not in the collection set, except abort case, we add another exception case check(region reserved for mark/compact) for copyForwardHybrid mode, the references could be NULL, which caused the failure.

This pull request has included the fix for the the failure.
the detail changes at below

bool
MM_CopyForwardScheme::isObjectInNoEvacuationRegions(MM_EnvironmentVLHGC *env, J9Object *objectPtr)
{
++ if ((NULL == objectPtr) || (0 == _regionCountCannotBeEvacuated)) {
++ return false;
++ }
MM_HeapRegionDescriptorVLHGC *region = (MM_HeapRegionDescriptorVLHGC *)_regionManager->tableDescriptorForAddress(objectPtr);
return region->_markData._noEvacuation;
}

[dmitripivkine]

Jenkins test sanity zLinux jdk8