counter-go

Go.dev github.com/jldec/counter-go

This package demonstrates 3 different implementations of a threadsafe global counter.

1. CounterAtomic uses atomic.AddUint64 and atomic.LoadUint64.
2. CounterMutex uses sync.RWMutex.
3. CounterChannel serializes all reads and writes inside 1 goroutine with 2 channels.

This was written to accompany the blog post Getting started with Goroutines and channels.

All 3 types implement the Counter interface:

type Counter interface {
    Get() uint32 // get current counter value
    Inc()        // increment by 1
}

Initialization

Call counter.NewCounterChannel() to use CounterChannel.
The other 2 do not require any initialization.

Benchmarks

$ go test -bench .
goos: darwin
goarch: amd64
pkg: github.com/jldec/counter-go
cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz

Simple: 1 op = 1 Inc() in same thread

BenchmarkCounter_1/Atomic-12                 195965660          6 ns/op
BenchmarkCounter_1/Mutex-12                   54177086         22 ns/op
BenchmarkCounter_1/Channel-12                  4499144        286 ns/op

Concurrent: 1 op = 1 Inc() across each of 10 goroutines

BenchmarkCounter_2/Atomic_no_reads-12          7298484        191 ns/op
BenchmarkCounter_2/Mutex_no_reads-12           1966656        621 ns/op
BenchmarkCounter_2/Channel_no_reads-12          256842       4771 ns/op

Concurrent: 1 op = [ 1 Inc() + 10 Get() ] across each of 10 goroutines

BenchmarkCounter_2/Atomic_10_reads-12          3922029        286 ns/op
BenchmarkCounter_2/Mutex_10_reads-12            416354       2844 ns/op
BenchmarkCounter_2/Channel_10_reads-12           21506      55733 ns/op

Constrained to single thread

$ GOMAXPROCS=1 go test -bench .

BenchmarkCounter_1/Atomic                    197135869          6 ns/op
BenchmarkCounter_1/Mutex                      55698454         22 ns/op
BenchmarkCounter_1/Channel                     5689788        214 ns/op

BenchmarkCounter_2/Atomic_no_reads            19519166         60 ns/op
BenchmarkCounter_2/Mutex_no_reads              4702759        254 ns/op
BenchmarkCounter_2/Channel_no_reads             530554       2197 ns/op

BenchmarkCounter_2/Atomic_10_reads             6269979        189 ns/op
BenchmarkCounter_2/Mutex_10_reads               927439       1354 ns/op
BenchmarkCounter_2/Channel_10_reads              47889      25054 ns/op