Add thundering herd tests

1 files changed, 86 insertions, 0 deletions

diff --git a/bench_test.go b/bench_test.go
index 82aaba1..08faa96 100644
--- a/bench_test.go
+++ b/bench_test.go
@@ -149,3 +149,89 @@ func BenchmarkPingPong(b *testing.B) {
 	b.ReportAllocs()
 	parallelPingPongs(b, 1)
 }
+
+const maxTokens = 25
+
+func BenchmarkThunderingHerdCondVar(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var mu sync.Mutex
+		consumer := sync.NewCond(&mu)
+		generator := sync.NewCond(&mu)
+		done := false
+		tokens := 0
+		var pending sync.WaitGroup
+		for range iter.N(1000) {
+			pending.Add(1)
+			go func() {
+				mu.Lock()
+				for {
+					if tokens > 0 {
+						tokens--
+						generator.Signal()
+						break
+					}
+					consumer.Wait()
+				}
+				mu.Unlock()
+				pending.Done()
+			}()
+		}
+		go func() {
+			mu.Lock()
+			for !done {
+				if tokens < maxTokens {
+					tokens++
+					consumer.Signal()
+				} else {
+					generator.Wait()
+				}
+			}
+			mu.Unlock()
+		}()
+		pending.Wait()
+		mu.Lock()
+		done = true
+		generator.Signal()
+		mu.Unlock()
+	}
+
+}
+
+func BenchmarkThunderingHerd(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		done := NewVar(false)
+		tokens := NewVar(0)
+		pending := NewVar(0)
+		for range iter.N(1000) {
+			Atomically(VoidOperation(func(tx *Tx) {
+				tx.Set(pending, tx.Get(pending).(int)+1)
+			}))
+			go func() {
+				Atomically(VoidOperation(func(tx *Tx) {
+					t := tx.Get(tokens).(int)
+					if t > 0 {
+						tx.Set(tokens, t-1)
+						tx.Set(pending, tx.Get(pending).(int)-1)
+					} else {
+						tx.Retry()
+					}
+				}))
+			}()
+		}
+		go func() {
+			for Atomically(func(tx *Tx) interface{} {
+				if tx.Get(done).(bool) {
+					return false
+				}
+				tx.Assert(tx.Get(tokens).(int) < maxTokens)
+				tx.Set(tokens, tx.Get(tokens).(int)+1)
+				return true
+			}).(bool) {
+			}
+		}()
+		Atomically(VoidOperation(func(tx *Tx) {
+			tx.Assert(tx.Get(pending).(int) == 0)
+		}))
+		AtomicSet(done, true)
+	}
+}