lock_test.go

package lock_test

import (
	"fmt"
	"sync"
	"testing"
	"time"
)

type rlocker interface {
	sync.Locker
	RLock()
	RUnlock()
}

type noopLock struct{}

func (m noopLock) Lock()    {}
func (m noopLock) Unlock()  {}
func (m noopLock) RLock()   {}
func (m noopLock) RUnlock() {}

type lockOnlyMutex struct {
	sync.Mutex
}

func (m *lockOnlyMutex) RLock()   { m.Lock() }
func (m *lockOnlyMutex) RUnlock() { m.Unlock() }

func BenchmarkLocks(b *testing.B) {
	mutexes := []rlocker{
		&noopLock{},
		&lockOnlyMutex{},
		&sync.RWMutex{},
	}

	for _, readRatio := range []int{1, 10, 100} {
		for _, mu := range mutexes {
			b.Run(fmt.Sprintf("%T,readRatio=%d", mu, readRatio), func(b *testing.B) {
				b.ResetTimer()
				benchmarkRLocker(b, mu, readRatio, time.Microsecond, time.Nanosecond)
			})
		}
	}
}

func benchmarkRLocker(b *testing.B, mu rlocker, readRatio int, readTime, writeTime time.Duration) {
	writers := 1
	readers := writers * readRatio

	// mu := sync.Mutex{}
	wg := sync.WaitGroup{}
	x := 0
	for i := 0; i < readers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for {
				mu.RLock()
				y := x
				time.Sleep(readTime)
				mu.RUnlock()
				if y > b.N {
					return
				}
			}
		}()
	}

	for i := 0; i < writers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for {
				// log.Printf("acquiring write lock")
				// defer log.Printf("releasing write lock")

				mu.Lock()
				time.Sleep(writeTime)
				x++
				done := x > b.N
				mu.Unlock()

				if done {
					return
				}
			}
		}()
	}

	wg.Wait()
}

Results:

goos: darwin
goarch: amd64
BenchmarkLocks/*lock_test.noopLock,readRatio=1-4         	 2000000	       968 ns/op
BenchmarkLocks/*lock_test.lockOnlyMutex,readRatio=1-4    	   20000	    129093 ns/op
BenchmarkLocks/*sync.RWMutex,readRatio=1-4               	  200000	      8627 ns/op
BenchmarkLocks/*lock_test.noopLock,readRatio=10-4        	  200000	      8337 ns/op
BenchmarkLocks/*lock_test.lockOnlyMutex,readRatio=10-4   	   10000	    533723 ns/op
BenchmarkLocks/*sync.RWMutex,readRatio=10-4              	  100000	     20316 ns/op
BenchmarkLocks/*lock_test.noopLock,readRatio=100-4       	   30000	     52709 ns/op
BenchmarkLocks/*lock_test.lockOnlyMutex,readRatio=100-4  	    2000	   1026620 ns/op
BenchmarkLocks/*sync.RWMutex,readRatio=100-4             	   20000	     75479 ns/op
PASS
ok  	command-line-arguments	23.929s