Project Loom - java virtual threads

• game of loom 2 - life and deadlock of a virtual thread
• java virtual threads vs kotlin coroutines
• java virtual threads
• prepare for what loom is ahead
• structured concurrency in Java
• ultimate guide to Java virtual threads

---

src: Project Loom: Modern Scalable Concurrency for the Java Platform By Alan Bateman

Abstract

An upgrade to Java’s concurrency model.

Virtual threads:

• not backed by OS thread
• managed by the Java runtime
• 200-300 bytes of metadata
• pay-as-you go stack in the Java heap
• M:N threading Lots of mis-usage of virtual threads:
• thinking that virtual threads are faster threads
• replacing platform threads with virtual threads rather than tasks with virtual threads
• changing the ThreadFactory for a thread pool, thus pooling virtual threads
• pinning issues and assuming that all uses of monitors must be replaced
• using warmup issues
• doing over complicated stuff
• misunderstanding as to where the performance benefits come from Migration guide:
• move to simpler blocking / synchronous code
• migrate tasks to virtual threads, not platform threads to virtual threads
• use semaphore or similar to limit concurrency
• don’t cache expensive objects in thread locals
• avoid lengthy and frequent pinning (for now anyways)
• Adoption of virtual threads Try to move away from thread locals. Prefer ScopedValue over Thread locals for “one-way” data transmission.

---

src: Programmation Concurrente et Asynchrone : Loom en Java 20 et 21 (José Paumard) - 2023-04-26