Eliminated memory allocations from client's DoTimeout and GetTimeout

client.go

@@ -468,14 +468,19 @@ func clientGetURLTimeout(dst []byte, url string, timeout time.Duration, c client
 	}
 }
 
+type clientURLResponse struct {
+	statusCode int
+	body       []byte
+	err        error
+}
+
 func clientGetURLTimeoutFreeConn(dst []byte, url string, timeout time.Duration, c clientDoer) (statusCode int, body []byte, err error) {
-	var ch chan error
+	var ch chan clientURLResponse
 	chv := errorChPool.Get()
 	if chv == nil {
-		ch = make(chan error, 1)
-	} else {
-		ch = chv.(chan error)
+		chv = make(chan clientURLResponse, 1)
 	}
+	ch = chv.(chan clientURLResponse)
 
 	req := acquireRequest()
 
@@ -486,29 +491,32 @@ func clientGetURLTimeoutFreeConn(dst []byte, url string, timeout time.Duration,
 	// Without this 'hack' the load on slow host could exceed MaxConns*
 	// concurrent requests, since timed out requests on client side
 	// usually continue execution on the host.
-	var statusCodeCopy int
-	var bodyCopy []byte
 	go func() {
-		var errCopy error
-		statusCodeCopy, bodyCopy, errCopy = doRequest(req, dst, url, c)
-		ch <- errCopy
+		statusCodeCopy, bodyCopy, errCopy := doRequest(req, dst, url, c)
+		ch <- clientURLResponse{
+			statusCode: statusCodeCopy,
+			body:       bodyCopy,
+			err:        errCopy,
+		}
 	}()
 
 	var tc *time.Timer
 	tcv := timerPool.Get()
 	if tcv == nil {
 		tc = time.NewTimer(timeout)
+		tcv = tc
 	} else {
 		tc = tcv.(*time.Timer)
 		initTimer(tc, timeout)
 	}
 
 	select {
-	case err = <-ch:
+	case resp := <-ch:
 		releaseRequest(req)
 		errorChPool.Put(chv)
-		statusCode = statusCodeCopy
-		body = bodyCopy
+		statusCode = resp.statusCode
+		body = resp.body
+		err = resp.err
 	case <-tc.C:
 		body = dst
 		err = ErrTimeout
@@ -625,10 +633,9 @@ func clientDoTimeoutFreeConn(req *Request, resp *Response, timeout time.Duration
 	var ch chan error
 	chv := errorChPool.Get()
 	if chv == nil {
-		ch = make(chan error, 1)
-	} else {
-		ch = chv.(chan error)
+		chv = make(chan error, 1)
 	}
+	ch = chv.(chan error)
 
 	// Make req and resp copies, since on timeout they no longer
 	// may be accessed.
@@ -651,6 +658,7 @@ func clientDoTimeoutFreeConn(req *Request, resp *Response, timeout time.Duration
 	tcv := timerPool.Get()
 	if tcv == nil {
 		tc = time.NewTimer(timeout)
+		tcv = tc
 	} else {
 		tc = tcv.(*time.Timer)
 		initTimer(tc, timeout)

client_timing_test.go

@@ -69,7 +69,37 @@ func acquireFakeServerConn(s []byte) *fakeClientConn {
 
 var fakeClientConnPool sync.Pool
 
-func BenchmarkClientGetFastServer(b *testing.B) {
+func BenchmarkClientGetTimeoutFastServer(b *testing.B) {
+	body := []byte("123456789099")
+	s := []byte(fmt.Sprintf("HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: %d\r\n\r\n%s", len(body), body))
+	c := &Client{
+		Dial: func(addr string) (net.Conn, error) {
+			return acquireFakeServerConn(s), nil
+		},
+	}
+
+	nn := uint32(0)
+	b.RunParallel(func(pb *testing.PB) {
+		url := fmt.Sprintf("http://foobar%d.com/aaa/bbb", atomic.AddUint32(&nn, 1))
+		var statusCode int
+		var bodyBuf []byte
+		var err error
+		for pb.Next() {
+			statusCode, bodyBuf, err = c.GetTimeout(bodyBuf[:0], url, time.Second)
+			if err != nil {
+				b.Fatalf("unexpected error: %s", err)
+			}
+			if statusCode != StatusOK {
+				b.Fatalf("unexpected status code: %d", statusCode)
+			}
+			if !bytes.Equal(bodyBuf, body) {
+				b.Fatalf("unexpected response body: %q. Expected %q", bodyBuf, body)
+			}
+		}
+	})
+}
+
+func BenchmarkClientDoFastServer(b *testing.B) {
 	body := []byte("012345678912")
 	s := []byte(fmt.Sprintf("HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: %d\r\n\r\n%s", len(body), body))
 	c := &Client{
@@ -97,7 +127,7 @@ func BenchmarkClientGetFastServer(b *testing.B) {
 	})
 }
 
-func BenchmarkNetHTTPClientGetFastServer(b *testing.B) {
+func BenchmarkNetHTTPClientDoFastServer(b *testing.B) {
 	body := []byte("012345678912")
 	s := []byte(fmt.Sprintf("HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: %d\r\n\r\n%s", len(body), body))
 	c := &http.Client{