Created
May 3, 2017 08:00
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Compare-and-swap VS mutex
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| package util | |
| import ( | |
| "sync" | |
| "sync/atomic" | |
| "testing" | |
| ) | |
| type cas struct { | |
| value int64 | |
| } | |
| func (c *cas) Add(i int64) { | |
| repeat := true | |
| var old int64 | |
| for repeat { | |
| old = c.value | |
| repeat = !atomic.CompareAndSwapInt64(&c.value, old, old+i) | |
| } | |
| } | |
| func (c *cas) Value() int64 { | |
| return c.value | |
| } | |
| type mutex struct { | |
| m sync.Mutex | |
| value int64 | |
| } | |
| func (c *mutex) Add(i int64) { | |
| c.m.Lock() | |
| c.value += i | |
| c.m.Unlock() | |
| } | |
| func (c *mutex) Value() int64 { | |
| return c.value | |
| } | |
| func bench(b *testing.B, routines int, cnt interface { | |
| Add(int64) | |
| Value() int64 | |
| }) { | |
| wg := sync.WaitGroup{} | |
| wg.Add(routines) | |
| for i := 0; i < routines; i++ { | |
| go func() { | |
| for i := 0; i < b.N; i++ { | |
| cnt.Add(1) | |
| } | |
| wg.Done() | |
| }() | |
| } | |
| wg.Wait() | |
| if int64(routines*b.N) != cnt.Value() { | |
| b.Logf("Expected %d but got %d", routines*b.N, cnt.Value()) | |
| b.Fail() | |
| } | |
| } | |
| func BenchmarkCas1(b *testing.B) { | |
| bench(b, 1, &cas{}) | |
| } | |
| func BenchmarkCas10(b *testing.B) { | |
| bench(b, 10, &cas{}) | |
| } | |
| func BenchmarkCas100(b *testing.B) { | |
| bench(b, 100, &cas{}) | |
| } | |
| func BenchmarkCas1000(b *testing.B) { | |
| bench(b, 1000, &cas{}) | |
| } | |
| func BenchmarkMutex1(b *testing.B) { | |
| bench(b, 1, &mutex{}) | |
| } | |
| func BenchmarkMutex10(b *testing.B) { | |
| bench(b, 10, &mutex{}) | |
| } | |
| func BenchmarkMutex100(b *testing.B) { | |
| bench(b, 100, &mutex{}) | |
| } | |
| func BenchmarkMutex1000(b *testing.B) { | |
| bench(b, 1000, &mutex{}) | |
| } | |
| // Results are: | |
| // | |
| // BenchmarkCas1-8 100000000 13.4 ns/op | |
| // BenchmarkCas10-8 1000000 1483 ns/op | |
| // BenchmarkCas100-8 100000 15414 ns/op | |
| // BenchmarkCas1000-8 10000 156046 ns/op | |
| // BenchmarkMutex1-8 50000000 27.2 ns/op | |
| // BenchmarkMutex10-8 1000000 1317 ns/op | |
| // BenchmarkMutex100-8 100000 14040 ns/op | |
| // BenchmarkMutex1000-8 10000 160975 ns/op |
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