Chapter 13Concurrency Primitives MeasuredPaid chapter

Channels — Implementation, Contention, the Memory Model, and Alternatives

Understand the runtime implementation of channels, their contention characteristics, the memory-model guarantee they provide, and when mutexes/atomics are measurably better.

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What this chapter teaches

Common belief

Channels are the idiomatic, fast way to share data; use them everywhere.

What actually happens

channel operations depend on state: successful transfers use runtime synchronization, failed nonblocking operations can return without locking, and blocking operations park. Compare equivalent coordination workloads before choosing a primitive.

Mechanisms covered

An unbuffered transfer can directly satisfy an already-waiting peer; the current goroutine parks only when it must wait. Buffered channels avoid handoff when neither full nor empty, but still lock per operation.

Under contention, the channel lock is the bottleneck. Atomics and mutexes avoid scheduler coordination.

Memory model: a send happens-before the corresponding receive completes; this establishes ordering across goroutines. That guarantee — not throughput — is the reason to choose a channel.

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