RFR: 8255232: G1: Make G1BiasedMappedArray freeable [v2]

[Kim Barrett]

On Thu, 29 Oct 2020 09:56:01 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I have reviews for this change that makes G1BiasedMappedArray freeable?
>> 
>> Previously all G1BiasedMappedArray were created as unfreeable i.e. assigned to static variables. However with JDK-8253600 I need one such biased map for the full collector which is created and deleted during full GC. So the biased array should also be freed as necessary to avoid a memory leak.
>> 
>> The alternative would be to statically allocate that map anyway and provide it to the current G1FullCollector instance, but I do not think the single malloc call is perf sensitive compared to full collector work and there is much point in doing something more complicated at this time. In the future I hope that the young gen collector will also be extracted from G1CollectedHeap with the same need. If/when allocation of these helper data structures becomes a problem I would suggest looking into this again.
>> 
>> One option then could be using some ResoureArea for these things in the future.
>> 
>> For this change there should be no change in behavior at all.
>> 
>> Testing: tier1-5
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   ayang review

Marked as reviewed by kbarrett (Reviewer).

-------------

PR: https://git.openjdk.java.net/jdk/pull/808