RFR: 8261743: Shenandoah: enable String deduplication with compact heuristics

[Aleksey Shipilev]

On Thu, 6 Nov 2025 01:38:36 GMT, Rui Li <duke at openjdk.org> wrote:

> Enable `UseStringDeduplication` when using compact heuristics.
> 
> Testing:
> 
> ./build/macosx-aarch64-server-release/images/jdk/bin/java -XX:+UseShenandoahGC -XX:+UnlockDiagnosticVMOptions -XX:ShenandoahGCHeuristics=compact -XX:+PrintFlagsFinal --version | grep UseStringDeduplication
>      bool UseStringDeduplication                   = true                                      {product} {default}
> 
> 
> Note: The labels should be `{product} {ergonomic}` ideally. Pending on a separate issue: [JDK-8371381](https://bugs.openjdk.org/browse/JDK-8371381)

Looks good. Have you measured any impact on pauses / GC durations in testing?

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28170#pullrequestreview-3427178962