ParallelGC provides PSChunkLargeArrays, a boolean VM command line product option.

This option controls whether the GC is permitted to split the processing of large objarrays into subtasks that can be worked on by multiple threads in parallel. This option, with its default true value, has been present in ParallelGC for a very long time. However, none of the other GCs provide such an option, instead (except for SerialGC) unconditionally permitting such splitting for sufficiently large objarrays.

The size of the parallel chunks (and the minimum size for splitting) is controlled by another VM product option, ParGCArrayScanChunk. Making this sufficiently large will implicitly disable the splitting, so we don't really need the boolean flag for that purpose anyway.

Internet searches for PSChunkLargeArrays didn't find anything suggesting it be disabled for any reason.