use pointers to optimise equalTopologies func

Author: isopov

x/mongo/driver/topology/topology.go

@@ -809,14 +809,14 @@ func equalTopologies(topo1, topo2 description.Topology) bool {
 		return false
 	}
 
-	topoServers := make(map[string]description.Server, len(topo1.Servers))
-	for _, s := range topo1.Servers {
-		topoServers[s.Addr.String()] = s
+	topoServers := make(map[string]*description.Server, len(topo1.Servers))
+	for i := range topo1.Servers {
+		topoServers[topo1.Servers[i].Addr.String()] = &topo1.Servers[i]
 	}
 
-	otherServers := make(map[string]description.Server, len(topo2.Servers))
-	for _, s := range topo2.Servers {
-		otherServers[s.Addr.String()] = s
+	otherServers := make(map[string]*description.Server, len(topo2.Servers))
+	for i := range topo2.Servers {
+		otherServers[topo2.Servers[i].Addr.String()] = &topo2.Servers[i]
 	}
 
 	if len(topoServers) != len(otherServers) {
@@ -826,7 +826,7 @@ func equalTopologies(topo1, topo2 description.Topology) bool {
 	for _, server := range topoServers {
 		otherServer := otherServers[server.Addr.String()]
 
-		if !driverutil.EqualServers(server, otherServer) {
+		if !driverutil.EqualServers(*server, *otherServer) {
 			return false
 		}
 	}

x/mongo/driver/topology/topology_test.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"path"
+	"strconv"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -1040,3 +1041,28 @@ func BenchmarkSelectServerFromDescription(b *testing.B) {
 		})
 	}
 }
+
+func BenchmarkEqualTopologies(b *testing.B) {
+	servers := make([]description.Server, 100)
+	for i := 0; i < len(servers); i++ {
+		servers[i] = description.Server{
+			Addr:              address.Address("127.0.0." + strconv.Itoa(i) + ":27017"),
+			HeartbeatInterval: time.Duration(10) * time.Second,
+			LastWriteTime:     time.Date(2017, 2, 11, 14, 0, 0, 0, time.UTC),
+			LastUpdateTime:    time.Date(2017, 2, 11, 14, 0, 2, 0, time.UTC),
+			Kind:              description.ServerKindMongos,
+			WireVersion:       &description.VersionRange{Min: 6, Max: 21},
+		}
+	}
+	desc := description.Topology{
+		Servers: servers,
+	}
+
+	b.ResetTimer()
+	b.RunParallel(func(p *testing.PB) {
+		b.ReportAllocs()
+		for p.Next() {
+			_ = equalTopologies(desc, desc)
+		}
+	})
+}