RFR: 8328792: Parallel: Refactor PSParallelCompact::summary_phase [v9]

[Ivan Walulya]

On Wed, 10 Apr 2024 08:07:20 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> The diff is not easy to follow; it's better to read the new code directly. `summary_phase` contains the gist of collecting live-size from each space, calculating dense-prefix and summarizing old-space using dense-prefix.
>> 
>> (There is slight improvement to the "Summary Phase", but it takes only ~0.01ms for either case.)
>
> Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:
> 
>   pgc-compute-dense-prefix

Changes requested by iwalulya (Reviewer).

src/hotspot/share/gc/parallel/psParallelCompact.cpp line 1143:

> 1141: 
> 1142:   if (maximum_compaction || is_old_gen_overflowing || is_interval_ended || is_region_full) {
> 1143:     _maximum_compaction_gc_num = total_invocations;

Based on the function name, we don't expect it to do more than `reassess_maximum_compaction`, additionally this modification also requires that we call `reassess_maximum_compaction` even when `maximum_compaction` is already true. Is is possible to decouple these two `reassess_maximum_compaction` and `_maximum_compaction_gc_num = total_invocations`?

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PR Review: https://git.openjdk.org/jdk/pull/18451#pullrequestreview-1991826848
PR Review Comment: https://git.openjdk.org/jdk/pull/18451#discussion_r1559526150