diff --git a/cmd/mtseeder/main.go b/cmd/mtseeder/main.go
index 0cbb0f9..38396a6 100644
--- a/cmd/mtseeder/main.go
+++ b/cmd/mtseeder/main.go
@@ -8,6 +8,8 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"os"
+	"runtime/pprof"
 
 	"bitbucket.org/s_l_teichmann/mtsatellite/common"
 )
@@ -27,6 +29,7 @@ func main() {
 		transparent      bool
 		transparentDim   float64
 		version          bool
+		cpuProfile       string
 	)
 
 	defaultBgColor := common.ColorToHex(common.BackgroundColor)
@@ -60,6 +63,7 @@ func main() {
 		"td", common.DefaultTransparentDim*100.0,
 		"Extra fimming of transparent nodes each depth meter in percent. (shorthand)")
 	flag.BoolVar(&version, "version", false, "Print version and exit.")
+	flag.StringVar(&cpuProfile, "c", "", "Dump pprof profile to file.")
 
 	flag.Parse()
 
@@ -67,6 +71,15 @@ func main() {
 		common.PrintVersionAndExit()
 	}
 
+	if cpuProfile != "" {
+		f, err := os.Create(cpuProfile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		pprof.StartCPUProfile(f)
+		defer pprof.StopCPUProfile()
+	}
+
 	bg := common.ParseColorDefault(bgColor, common.BackgroundColor)
 
 	if !skipBaseLevel {
diff --git a/cmd/mtwebmapper/web/index.html b/cmd/mtwebmapper/web/index.html
index 85345af..dd26a91 100644
--- a/cmd/mtwebmapper/web/index.html
+++ b/cmd/mtwebmapper/web/index.html
@@ -48,7 +48,7 @@
     <script type="text/javascript" src="js/leaflet.awesome-markers.js"></script>
     <script>
 
-var useWebsocket = false; // Set to true if you want websocket support
+var useWebsocket = true; // Set to true if you want websocket support
 
 L.Projection.NoWrap = {
     project: function (latlng) {
diff --git a/common/basetilecreator.go b/common/basetilecreator.go
index ee70a79..7a8a39b 100644
--- a/common/basetilecreator.go
+++ b/common/basetilecreator.go
@@ -90,23 +90,23 @@ func (btc *BaseTileCreator) Close() error {
 	return btc.client.Close()
 }
 
+func (btc *BaseTileCreator) drawBlock(block *Block) {
+	if err := btc.yOrder.RenderBlock(block, btc.colors); err != nil {
+		log.Printf("WARN: rendering block failed: %s\n", err)
+	}
+}
+
 func (btc *BaseTileCreator) CreateTile(x, z int16, i, j int) (bool, error) {
 	btc.renderer.Reset()
 	btc.renderer.SetPos(x, z)
 	btc.yOrder.Reset()
 
-	drawBlock := func(block *Block) {
-		if err := btc.yOrder.RenderBlock(block, btc.colors); err != nil {
-			log.Printf("WARN: rendering block failed: %s\n", err)
-		}
-	}
-
 	var c1, c2 Coord
 
-	nareas := make([]Area, 0, tileWidth*tileHeight/2)
-	oareas := make([]Area, 1, tileWidth*tileHeight/2)
+	oareas := make([]Area, 0, tileWidth*tileHeight/2)
+	nareas := make([]Area, 1, tileWidth*tileHeight/2)
 
-	oareas[0] = Area{
+	nareas[0] = Area{
 		X1: 0, Z1: 0,
 		X2: int16(tileWidth) - 1, Z2: int16(tileHeight) - 1}
 
@@ -114,14 +114,11 @@ func (btc *BaseTileCreator) CreateTile(x, z int16, i, j int) (bool, error) {
 		if yRange[0] > btc.yMax || yRange[1] < btc.yMin {
 			continue
 		}
+
 		c1.Y = max16(yRange[0], btc.yMin)
 		c2.Y = min16(yRange[1], btc.yMax)
 
-		nareas = btc.renderer.UncoveredAreas(nareas, oareas)
-
-		if len(nareas) == 0 {
-			break
-		}
+		var allCount int
 
 		for _, area := range nareas {
 			c1.X = area.X1 + x
@@ -129,14 +126,23 @@ func (btc *BaseTileCreator) CreateTile(x, z int16, i, j int) (bool, error) {
 			c2.X = area.X2 + x
 			c2.Z = area.Z2 + z
 			query := Cuboid{P1: c1, P2: c2}
-			if err := btc.client.QueryCuboid(query, drawBlock); err != nil {
+			var count int
+			var err error
+			if count, err = btc.client.QueryCuboid(query, btc.drawBlock); err != nil {
 				return false, err
 			}
-			if err := btc.yOrder.Drain(btc.colors); err != nil {
+			allCount += count
+			if err = btc.yOrder.Drain(btc.colors); err != nil {
 				log.Printf("WARN: rendering block failed: %s\n", err)
 			}
 		}
-		oareas, nareas = nareas, oareas[0:0]
+		if allCount > 0 {
+			xareas := btc.renderer.UncoveredAreas(oareas, nareas)
+			if len(xareas) == 0 {
+				break
+			}
+			nareas, oareas = xareas, nareas[:0]
+		}
 	}
 
 	path := filepath.Join(btc.baseDir, strconv.Itoa(i), strconv.Itoa(j)+".png")
diff --git a/common/redisclient.go b/common/redisclient.go
index d792cc1..4f977db 100644
--- a/common/redisclient.go
+++ b/common/redisclient.go
@@ -144,7 +144,7 @@ func (client *RedisClient) readBulkString(data *[]byte) (size int, err error) {
 	return
 }
 
-func (client *RedisClient) QueryCuboid(cuboid Cuboid, fn func(*Block)) (err error) {
+func (client *RedisClient) QueryCuboid(cuboid Cuboid, fn func(*Block)) (count int, err error) {
 	p1 := CoordToPlain(cuboid.P1)
 	p2 := CoordToPlain(cuboid.P2)
 	if err = client.writeHSpatial(p1, p2); err != nil {
@@ -157,7 +157,7 @@ func (client *RedisClient) QueryCuboid(cuboid Cuboid, fn func(*Block)) (err erro
 		key   int64
 	)
 
-	for {
+	for ; ; count++ {
 		if size, err = client.readBulkString(&data); err != nil {
 			return
 		}