RFR: 8272609: Add string deduplication support to SerialGC [v10]

[Albert Mingkun Yang]

On Sat, 21 Aug 2021 19:09:35 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> I believe it's desirable to narrow the request window (btw first `add` and `flush`), which offers more prompt string-dedup and memory release (in `flush`). Additionally, it makes more sense to call `flush` right after the complete live objects traversal  (strong-marking + final-marking as part of ref-processing), since we will not visit any new objects then.
>
> I prefer it where it is.  Rather than putting something between phantom
> reference processing an oopstorage-based weak processing, I would prefer to
> merge those two.  I don't remember if there's an RFE for that.

I still think `flush` should be called sooner, e.g. inside `mark_sweep_phase1`, which is not in conflict with merging phantom-processing and weak root processing. Anyway, this is subjective; feel free to integrate the current version.

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PR: https://git.openjdk.java.net/jdk/pull/5153