RFR: 8259776: Remove ParallelGC non-CAS oldgen allocation [v2]

[Kim Barrett]

> On Jan 18, 2021, at 5:23 AM, Thomas Schatzl <tschatzl at openjdk.java.net> wrote:
> src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp line 404:
> 
>> 402:   if (!should_alloc_in_eden(size) || GCLocker::is_active_and_needs_gc()) {
>> 403:     // Size is too big for eden, or gc is locked out.
>> 404:     return old_gen()->allocate_and_record(size);
> 
> I would have kind of preferred if `allocate_and_record` were a helper method here in `ParallelScavengeHeap` since the recording seems to be entirely a thing of the PSH and not of the old gen, and the implementation of that method just calls back in here, but I am good with this too.

I like this suggestion.