Threading

The move from a small trading firm to a large financial institution meant working with codebases an order of magnitude larger, maintained by dozens of engineers across multiple teams. It also meant encountering the full spectrum of Java threading models in production — some appropriate, some inherited from a different era, and some that were actively causing problems. This is a survey of what those models look like, what they’re good at, and how you tell which one a system needs. ...

When a thread is waiting for work — a new event, a lock to release, a signal — it has two options. It can block (tell the OS “wake me up when there’s work”) or busy-spin (loop checking a condition, never yielding the CPU). Both are correct. They have very different performance profiles. ...