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

[Thomas Schatzl]

> 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

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/808/files
  - new: https://git.openjdk.java.net/jdk/pull/808/files/51b297bb..c6835bae

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=808&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=808&range=00-01

  Stats: 9 lines in 1 file changed: 0 ins; 8 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/808.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/808/head:pull/808

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