RFR: 8264718: Shenandoah: enable string deduplication during root scanning

[王超]

On Mon, 5 Apr 2021 21:42:32 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Shenandoah used to scan roots at pauses, so it deliberately disables string deduplication during root scanning to avoid extra pause times.
> 
> Now, Shenandoah scans roots in concurrent phase, it is no longer a concern, we should enable it.
> 
> Test:
> - [x] hotspot_gc_shenandoah

src/hotspot/share/gc/shenandoah/shenandoahSTWMark.cpp line 134:

> 132:     ShenandoahInitMarkRootsClosure<ENQUEUE_DEDUP>  init_mark(task_queues()->queue(worker_id));
> 133:     _root_scanner.roots_do(&init_mark, worker_id);
> 134: 

extra empty line

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PR: https://git.openjdk.java.net/jdk/pull/3348