RFR: Use PLABs for old gen allocations, including promotions. [v2]

[earthling-amzn]

On Fri, 16 Apr 2021 14:28:20 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> Bernd Mathiske has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Register filler objects for unsuccessful non-LAB evacuations.
>
> src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp line 430:
> 
>> 428: 
>> 429:   assert(r->is_empty(), "Region must be empty after flipping from mutator to GC.");
>> 430:   r->set_affiliation(FREE);
> 
> Why is this block needed now?

I think this could be an assert. The region should already be `FREE` at this point.

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PR: https://git.openjdk.java.net/shenandoah/pull/30