[go-nuts] use http.ResponseWriter Write() to take payload as http response,the http server's QPS is very low

when I use http.ResponseWriter Write() to take payload as http response, in
boom test the http server's QPS is just 7000~8000,but if I only set header,
in boom test the QPS is up to 40000. is the http.ResponseWriter Write() is
enefficiency?
here is my test code:

func handleHeader(w http.ResponseWriter, r *http.Request) {
     w.Header().Set("Content-Length", "0")
}

func handlePayload50(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Length", "50")
    w.Write(make([]byte, 50))
}

func handlePayload128(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Length", "128")
    w.Write(make([]byte, 128))
}

func handlePayload1024(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Length", "1024")
    w.Write(make([]byte, 1024))
}

func main() {
    runtime.GOMAXPROCS(runtime.NumCPU())
    http.HandleFunc("/header", handleHeader)
    http.HandleFunc("/payload50", handlePayload50)
    http.HandleFunc("/payload128", handlePayload128)
    http.HandleFunc("/payload1024", handlePayload1024)
    host := fmt.Sprintf("%s:%d", "0.0.0.0", 5001)
    http.ListenAndServe(host, nil)
}


and the boom test result:
./boom -c 1000 -n 500000 -cpus 12 http://192.168.0.2:5001/header
500000 / 500000 Boooooooooooooooooooooooooooooooooooooooooooooooooooo!
100.00 %

Summary:
   Total: 12.8799 secs.
   Slowest: 3.2799 secs.
   Fastest: 0.0018 secs.
   Average: 0.0239 secs.
   Requests/sec: 38810.4907

Status code distribution:
   [200] 499875 responses

Response time histogram:
   0.002 [1] |
   0.330 [499306] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
   0.657 [0] |
   0.985 [0] |
   1.313 [312] |
   1.641 [0] |
   1.969 [0] |
   2.297 [0] |
   2.624 [0] |
   2.952 [0] |
   3.280 [256] |

Latency distribution:
   10% in 0.0125 secs.
   25% in 0.0172 secs.
   50% in 0.0216 secs.
   75% in 0.0257 secs.
   90% in 0.0295 secs.
   95% in 0.0327 secs.
   99% in 0.0549 secs.

Error distribution:
   [125] Get http://192.168.0.2:5001/header: dial tcp 192.168.0.2:5001:
connection timed out

./boom -c 500 -n 500000 -cpus 12 http://192.168.0.2:5001/payload128
500000 / 500000 Boooooooooooooooooooooooooooooooooooooooooooooooooooo!
100.00 %

Summary:
   Total: 62.5205 secs.
   Slowest: 3.0714 secs.
   Fastest: 0.0112 secs.
   Average: 0.0601 secs.
   Requests/sec: 7997.1501
   Total Data Received: 63998208 bytes.
   Response Size per Request: 128 bytes.

Status code distribution:
   [200] 499986 responses

Response time histogram:
   0.011 [1] |
   0.317 [495652] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
   0.623 [0] |
   0.929 [0] |
   1.235 [4092] |
   1.541 [0] |
   1.847 [0] |
   2.153 [0] |
   2.459 [0] |
   2.765 [0] |
   3.071 [241] |

Latency distribution:
   10% in 0.0405 secs.
   25% in 0.0436 secs.
   50% in 0.0481 secs.
   75% in 0.0546 secs.
   90% in 0.0629 secs.
   95% in 0.0731 secs.
   99% in 0.1054 secs.

Error distribution:
   [14] Get http://192.168.0.2:5001/payload128: dial tcp 192.168.0.2:5001:
connection timed out