Game of Loom 2: life and dead(lock) of a virtual thread

on YouTube ↗47m

" summary

Virtual threads in JVM 21 are stable but carry concrete limits: experiments running 64 CPU-bound tasks on an 8-core machine show groups of eight virtual threads hogging a core due to non‑preemption, and a JMH benchmark with 100 workloads measures virtual threads as twice as slow because mounting/unmounting dominates time. ThreadLocal usage explodes memory with millions of virtual threads so scoped values are needed; carrier behavior is fixed (carrier thread pool is fixed to ForkJoin) and swapping it for an event-loop carrier causes a surprising single-lock deadlock.

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" chapters (9)

1. 0:00Introduction
2. 1:53Virtual threads overview
3. 6:15Limitations and challenges
4. 11:42CPU bound task concerns
5. 17:43Scheduling and cost
6. 23:29Thread locals and scope
7. 28:51Resource management pitfalls
8. 36:13Event loops and deadlocks
9. 44:06Conclusion

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