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

[Stefan Johansson]

On Wed, 21 Oct 2020 19:49:03 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> 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.cpp line 565:
> 
>> 563:   size_t old_gen_used = ParallelScavengeHeap::heap()->old_gen()->used_in_bytes();
>> 564:   size_t block_size = ParallelScavengeHeap::heap()->old_gen()->iterate_block_size();
>> 565:   uint n_blocks_in_old = old_gen_used / block_size + 1;
> 
> Instead of doing this calculation here, what do you think about making `iterate_block_size()` a constant in `PSOldGen` and instead adding a function that returns the number of blocks available, something like:
> `iterable_blocks()`

One additional thing here, the `n_blocks_in_old` calculation will return one extra block when old_gen_used is a multiple of block_size. : Here's an alternative:
  uint n_blocks_in_old = (old_gen_used + block_size - 1) / block_size;

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