8360024: Reorganize GC VM operations and implement is_gc_operation

[JonasNorlinder]

JDK-8359110 introduces a need to be able to categorize VM operations to be able to track GC activity in the VM thread for CPU time tracking. This patch will reorganize the shared GC VM operations in gcVMOperations.hpp to make a distinction between GC operations and serviceability/CDS etc. operations performed in the VM thread for the GC.

Additionally the ability to query is_gc_operation() is introduced in the base class VM_Operation and overridden in appropriate VM operations. This provides a clear and efficient interface to query the category of a VM operation.

Proposed changes in the shared class hierarchy:

//  VM_Operation
//    VM_Heap_Sync_Operation
//      VM_GC_Operation
//        VM_GC_Collect_Operation
//          VM_SerialGCCollect
//          VM_ParallelGCCollect
//          VM_CollectForAllocation
//            VM_SerialCollectForAllocation
//            VM_ParallelCollectForAllocation
//          VM_CollectForMetadataAllocation
//        VM_GC_Service_Operation
//          VM_GC_HeapInspection
//      VM_Verify
//      VM_PopulateDynamicDumpSharedSpace
//      VM_PopulateDumpSharedSpace

Renaming VM_GC_Sync_Operation to VM_Heap_Sync_Operation to make it clear that not all sub-classes is related to GC (shout-out to @kstefanj / @stefank for that suggestion). While VM_GC_HeapInspection is a serviceability operation it attempts to trigger a collection, hence it is put underneath VM_GC_Collect_Operation->VM_GC_Service_Operation. However only classes that inherits from VM_GC_Collect_Operation are considered to return true for is_gc_operation() as VM_GC_HeapInspection is considered to not belong to "GC activity".

ZGC and Shenandoah do not use sub-classing of VM_Heap_Sync_Operation, but their respective base classes and special classes for GC activity are marked as returning true for is_gc_operation().

The only is_XX_operation that is specified in VM_Operation is is_gc_operation to not clutter with cases that are not used (is_gc_operation will be used by JDK-8359110). That being said, these behavioral queries may be extended in case we want to explore CPU time tracking beyond the GC component.

Note: PR for JDK-8359110 already contains a proposal for is_gc_operation but it was deemed that it was more appropriate to bring along that change during reorganization of GC VM operations since implementing it at the correct places without this change would require a lot more overrides...

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Progress

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Issue

• JDK-8360024: Reorganize GC VM operations and implement is_gc_operation (Enhancement - P4)

Reviewers

• David Holmes (@dholmes-ora - Reviewer) 🔄 Re-review required (review applies to 7c8e6d81)

Reviewing

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[bridgekeeper]

👋 Welcome back JonasNorlinder! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[JonasNorlinder]

/label add hotspot-gc hotspot-runtime

[openjdk]

@JonasNorlinder This change is no longer ready for integration - check the PR body for details.

[openjdk]

@JonasNorlinder
The hotspot-gc label was successfully added.

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[mlbridge]

Webrevs

• 01: Full - Incremental (7faaf506)
• 00: Full (7c8e6d81)

[dholmes-ora]

This looks quite reasonable to me. Obviously GC folk get final approval.

One minor nit.

[JonasNorlinder]

Thanks for the review @dholmes-ora.