ringbuffer: eliminate idle load by using condition variables instead of sleeps

pkg/ringbuffer/event.go

@@ -0,0 +1,38 @@
+package ringbuffer
+
+import (
+	"sync"
+)
+
+type event struct {
+	mutex sync.Mutex
+	cond  *sync.Cond
+	value bool
+}
+
+func newEvent() *event {
+	cv := &event{}
+	cv.cond = sync.NewCond(&cv.mutex)
+	return cv
+}
+
+func (cv *event) signal() {
+	func() {
+		cv.mutex.Lock()
+		defer cv.mutex.Unlock()
+		cv.value = true
+	}()
+
+	cv.cond.Broadcast()
+}
+
+func (cv *event) wait() {
+	cv.mutex.Lock()
+	defer cv.mutex.Unlock()
+
+	if !cv.value {
+		cv.cond.Wait()
+	}
+
+	cv.value = false
+}