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Pinning & JEP 491

When virtual threads pin carrier threads, how to spot it in dumps, and what Java 24 changed.

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Read these first

Spot pinning in dumps

Look for a virtual thread stuck in RUNNABLE inside synchronized while carriers are saturated. Few carriers + many mounted virtual threads = throughput collapse.

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Still to come · 2 sections

  • Java 21 vs Java 24
  • Interview one-liner

Test yourself

Answer these before moving on — recall is what makes it stick.