This is the JVM false-sharing problem in a different language. The rules differ slightly, the tooling differs, but the underlying hardware constraint — cache lines are 64 bytes and sharing one across goroutines is expensive — is identical. ...
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. ...
Martin Thompson coined the term “mechanical sympathy” — the idea that to write fast software you need to understand the machine it runs on. Not at the assembly level necessarily, but well enough to reason about what the CPU, memory hierarchy, and OS are actually doing with your code. This post is what that looks like in practice, writing Java for a system where microseconds matter. ...