recycle pcb in next waitio

watcher.go

@@ -51,6 +51,7 @@ type watcher struct {
 	pendingCreate     []*aiocb
 	pendingProcessing []*aiocb // swaped pending
 	pendingMutex      sync.Mutex
+	recycles          []*aiocb
 
 	// IO-completion events to user
 	chResults chan *aiocb
@@ -179,15 +180,21 @@ func (w *watcher) notifyPending() {
 // WaitIO blocks until any read/write completion, or error.
 // An internal 'buf' returned or 'r []OpResult' are safe to use BEFORE next call to WaitIO().
 func (w *watcher) WaitIO() (r []OpResult, err error) {
+	// recycle previous aiocb
+	for k := range w.recycles {
+		aiocbPool.Put(w.recycles[k])
+	}
+	w.recycles = w.recycles[:0]
+
 	for {
 		select {
 		case pcb := <-w.chResults:
 			r = append(r, OpResult{Operation: pcb.op, Conn: pcb.conn, IsSwapBuffer: pcb.useSwap, Buffer: pcb.buffer, Size: pcb.size, Error: pcb.err, Context: pcb.ctx})
-			aiocbPool.Put(pcb)
+			w.recycles = append(w.recycles, pcb)
 			for len(w.chResults) > 0 {
 				pcb := <-w.chResults
 				r = append(r, OpResult{Operation: pcb.op, Conn: pcb.conn, IsSwapBuffer: pcb.useSwap, Buffer: pcb.buffer, Size: pcb.size, Error: pcb.err, Context: pcb.ctx})
-				aiocbPool.Put(pcb)
+				w.recycles = append(w.recycles, pcb)
 			}
 
 			atomic.CompareAndSwapInt32(&w.shouldSwap, 0, 1)