net/http: add parallel client/server benchmark

R=bradfitz@golang.org

R=bradfitz
CC=bradfitz, dave, dsymonds, gobot, golang-dev
https://golang.org/cl/6441134

src/pkg/net/http/serve_test.go

@@ -22,8 +22,11 @@ import (
 	"os"
 	"os/exec"
 	"reflect"
+	"runtime"
 	"strconv"
 	"strings"
+	"sync"
+	"sync/atomic"
 	"syscall"
 	"testing"
 	"time"
@@ -1281,6 +1284,50 @@ func BenchmarkClientServer(b *testing.B) {
 	b.StopTimer()
 }
 
+func BenchmarkClientServerParallel4(b *testing.B) {
+	benchmarkClientServerParallel(b, 4)
+}
+
+func BenchmarkClientServerParallel64(b *testing.B) {
+	benchmarkClientServerParallel(b, 64)
+}
+
+func benchmarkClientServerParallel(b *testing.B, conc int) {
+	b.StopTimer()
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, r *Request) {
+		fmt.Fprintf(rw, "Hello world.\n")
+	}))
+	defer ts.Close()
+	b.StartTimer()
+
+	numProcs := runtime.GOMAXPROCS(-1) * conc
+	var wg sync.WaitGroup
+	wg.Add(numProcs)
+	n := int32(b.N)
+	for p := 0; p < numProcs; p++ {
+		go func() {
+			for atomic.AddInt32(&n, -1) >= 0 {
+				res, err := Get(ts.URL)
+				if err != nil {
+					b.Logf("Get: %v", err)
+					continue
+				}
+				all, err := ioutil.ReadAll(res.Body)
+				if err != nil {
+					b.Logf("ReadAll: %v", err)
+					continue
+				}
+				body := string(all)
+				if body != "Hello world.\n" {
+					panic("Got body: " + body)
+				}
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+}
+
 // A benchmark for profiling the server without the HTTP client code.
 // The client code runs in a subprocess.
 //