RFR: 8267257: Shenandoah: Always deduplicate strings when it is enabled during full gc

[Roman Kennke]

On Tue, 18 May 2021 15:18:32 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Full GC should recover as much memory as possible, so it should deduplicate all string candidates regardless their ages, when it is enabled. Also enhanced TestStringDedup.java test to ensure all candidates are deduplicated.
> 
> Note: Full GC does not preserve age bits, so current implementation will not deduplicate any strings even with back-to-back full GCs.
> 
> Test:
> - [x] hotspot_gc_shenandoah

Looks good to me. Thank you!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4096