Ruby Thread Contention: It's Not a Free-for-All

For a long time, I misunderstood "thread contention" in Ruby. It's not a chaotic struggle; instead, Ruby threads politely queue for the Global VM Lock (GVL). Each thread gets the GVL, executes code, and then releases it or is preempted after a certain time (the thread quantum, defaulting to 100ms). This happens when a thread performs I/O or runs longer than its quantum. Understanding this is crucial for optimizing multithreaded applications, especially to avoid CPU-bound threads blocking I/O-bound threads, leading to increased tail latency. Lowering the priority of CPU-bound threads or reducing the thread quantum can help, but the minimum slice is 10ms.