PythonWise

Go's concurrency unit is a goroutine, the Go runtime multiplexes goroutines to operating system (OS) threads. At an upper level, the OS maps threads to CPUs (or cores). To see this goroutine/thread migration, you'll need to use some C code (note that this is Linux specific).


If you run this code and sort the output, you'll see the workers moving between cores:
$ go run affinity.go | sort -u
worker: 0, CPU: 0
worker: 0, CPU: 1
worker: 0, CPU: 2
worker: 0, CPU: 3
worker: 1, CPU: 0
worker: 1, CPU: 1
worker: 1, CPU: 2
worker: 1, CPU: 3
worker: 2, CPU: 0
worker: 2, CPU: 1
worker: 2, CPU: 2
worker: 2, CPU: 3
worker: 3, CPU: 0
worker: 3, CPU: 1
worker: 3, CPU: 2
worker: 3, CPU: 3
Now if you run our code with the LOCK environment variable set, you can see each worker is pinned to a specific core.
$ LOCK=1 go run affinity.go | sort -u
worker: 0, CPU: 0
worker: 1, CPU: 1
worker: 2, CPU: 2
worker: 3, CPU: 3