1 files changed, 72 insertions, 0 deletions
diff --git a/src/sync/runtime_sema_test.go b/src/sync/runtime_sema_test.go
new file mode 100644
index 000000000..5b7dd3df3
--- /dev/null
+++ b/src/sync/runtime_sema_test.go
@@ -0,0 +1,72 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sync_test
+
+import (
+	"runtime"
+	. "sync"
+	"testing"
+)
+
+func BenchmarkSemaUncontended(b *testing.B) {
+	type PaddedSem struct {
+		sem uint32
+		pad [32]uint32
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		sem := new(PaddedSem)
+		for pb.Next() {
+			Runtime_Semrelease(&sem.sem)
+			Runtime_Semacquire(&sem.sem)
+		}
+	})
+}
+
+func benchmarkSema(b *testing.B, block, work bool) {
+	sem := uint32(0)
+	if block {
+		done := make(chan bool)
+		go func() {
+			for p := 0; p < runtime.GOMAXPROCS(0)/2; p++ {
+				Runtime_Semacquire(&sem)
+			}
+			done <- true
+		}()
+		defer func() {
+			<-done
+		}()
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		foo := 0
+		for pb.Next() {
+			Runtime_Semrelease(&sem)
+			if work {
+				for i := 0; i < 100; i++ {
+					foo *= 2
+					foo /= 2
+				}
+			}
+			Runtime_Semacquire(&sem)
+		}
+		_ = foo
+		Runtime_Semrelease(&sem)
+	})
+}
+
+func BenchmarkSemaSyntNonblock(b *testing.B) {
+	benchmarkSema(b, false, false)
+}
+
+func BenchmarkSemaSyntBlock(b *testing.B) {
+	benchmarkSema(b, true, false)
+}
+
+func BenchmarkSemaWorkNonblock(b *testing.B) {
+	benchmarkSema(b, false, true)
+}
+
+func BenchmarkSemaWorkBlock(b *testing.B) {
+	benchmarkSema(b, true, true)
+}