RFR: 8252103: Parallel heap inspection for ParallelScavengeHeap [v4]

[Stefan Johansson]

On Mon, 19 Oct 2020 13:09:34 GMT, Lin Zang <lzang at openjdk.org> wrote:

>> - Parallel heap iteration support for PSS
>> - JBS:  https://bugs.openjdk.java.net/browse/JDK-8252103
>
> Lin Zang has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.

src/hotspot/share/gc/parallel/parallelScavengeHeap.hpp line 318:

> 316:   static const uint eden_index = 0;
> 317:   static const uint survivor_index = 1;
> 318:   static const uint num_inseparable_spaces = 2;

One more comment. These should be CamelCase, and I have an idea to get rid of `num_inseparable_spaces`. 

If we make `_claimed_index` an integral type we could define `EdenIndex = -2` and `SurvivorIndex = -1`. If we then initialize `_claimed_index = EdenIndex` the old gen indices will be correct without needing a decrease.

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PR: https://git.openjdk.java.net/jdk/pull/25