diff --git a/cluster.go b/cluster.go
index 7a1af143..8c404c9c 100644
--- a/cluster.go
+++ b/cluster.go
@@ -8,6 +8,7 @@ import (
 	"math"
 	"math/rand"
 	"net"
+	"runtime"
 	"sort"
 	"sync"
 	"sync/atomic"
@@ -82,6 +83,10 @@ func (opt *ClusterOptions) init() {
 		opt.ReadOnly = true
 	}
 
+	if opt.PoolSize == 0 {
+		opt.PoolSize = 5 * runtime.NumCPU()
+	}
+
 	switch opt.ReadTimeout {
 	case -1:
 		opt.ReadTimeout = 0
diff --git a/command.go b/command.go
index 992e6143..7fcbe5a9 100644
--- a/command.go
+++ b/command.go
@@ -46,14 +46,15 @@ func firstCmdsErr(cmds []Cmder) error {
 }
 
 func writeCmd(cn *pool.Conn, cmds ...Cmder) error {
-	cn.Wb.Reset()
+	cn.WB.Reset()
 	for _, cmd := range cmds {
-		if err := cn.Wb.Append(cmd.Args()); err != nil {
+		err := cn.WB.Append(cmd.Args())
+		if err != nil {
 			return err
 		}
 	}
 
-	_, err := cn.Write(cn.Wb.Bytes())
+	_, err := cn.Write(cn.WB.Flush())
 	return err
 }
 
diff --git a/internal/pool/conn.go b/internal/pool/conn.go
index acaf3665..f39f2658 100644
--- a/internal/pool/conn.go
+++ b/internal/pool/conn.go
@@ -14,7 +14,7 @@ type Conn struct {
 	netConn net.Conn
 
 	Rd *proto.Reader
-	Wb *proto.WriteBuffer
+	WB *proto.WriteBuffer
 
 	Inited bool
 	usedAt atomic.Value
@@ -23,9 +23,10 @@ type Conn struct {
 func NewConn(netConn net.Conn) *Conn {
 	cn := &Conn{
 		netConn: netConn,
-		Wb:      proto.NewWriteBuffer(),
 	}
-	cn.Rd = proto.NewReader(cn.netConn)
+	buf := proto.NewBufioReader(netConn)
+	cn.Rd = proto.NewReader(buf)
+	cn.WB = proto.NewWriteBuffer(buf)
 	cn.SetUsedAt(time.Now())
 	return cn
 }
diff --git a/internal/pool/pool.go b/internal/pool/pool.go
index cab66904..b7b383be 100644
--- a/internal/pool/pool.go
+++ b/internal/pool/pool.go
@@ -246,8 +246,8 @@ func (p *ConnPool) popIdle() *Conn {
 }
 
 func (p *ConnPool) Put(cn *Conn) {
-	buf := cn.Rd.PeekBuffered()
-	if buf != nil {
+	buf := cn.Rd.Bytes()
+	if len(buf) > 0 {
 		internal.Logf("connection has unread data: %.100q", buf)
 		p.Remove(cn)
 		return
diff --git a/internal/proto/bufio_reader.go b/internal/proto/bufio_reader.go
new file mode 100644
index 00000000..6e392e6c
--- /dev/null
+++ b/internal/proto/bufio_reader.go
@@ -0,0 +1,231 @@
+package proto
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"io"
+)
+
+const defaultBufSize = 4096
+
+type BufioReader struct {
+	buf  []byte
+	rd   io.Reader // reader provided by the client
+	r, w int       // buf read and write positions
+	err  error
+}
+
+func NewBufioReader(rd io.Reader) *BufioReader {
+	r := new(BufioReader)
+	r.reset(make([]byte, defaultBufSize), rd)
+	return r
+}
+
+func (b *BufioReader) Reset(rd io.Reader) {
+	b.reset(b.buf, rd)
+}
+
+func (b *BufioReader) Buffer() []byte {
+	return b.buf
+}
+
+func (b *BufioReader) ResetBuffer(buf []byte) {
+	b.reset(buf, b.rd)
+}
+
+func (b *BufioReader) reset(buf []byte, rd io.Reader) {
+	*b = BufioReader{
+		buf: buf,
+		rd:  rd,
+	}
+}
+
+// Buffered returns the number of bytes that can be read from the current buffer.
+func (b *BufioReader) Buffered() int { return b.w - b.r }
+
+func (b *BufioReader) Bytes() []byte {
+	return b.buf[b.r:b.w]
+}
+
+var errNegativeRead = errors.New("bufio: reader returned negative count from Read")
+
+// fill reads a new chunk into the buffer.
+func (b *BufioReader) fill() {
+	// Slide existing data to beginning.
+	if b.r > 0 {
+		copy(b.buf, b.buf[b.r:b.w])
+		b.w -= b.r
+		b.r = 0
+	}
+
+	if b.w >= len(b.buf) {
+		panic("bufio: tried to fill full buffer")
+	}
+
+	// Read new data: try a limited number of times.
+	const maxConsecutiveEmptyReads = 100
+	for i := maxConsecutiveEmptyReads; i > 0; i-- {
+		n, err := b.rd.Read(b.buf[b.w:])
+		if n < 0 {
+			panic(errNegativeRead)
+		}
+		b.w += n
+		if err != nil {
+			b.err = err
+			return
+		}
+		if n > 0 {
+			return
+		}
+	}
+	b.err = io.ErrNoProgress
+}
+
+func (b *BufioReader) readErr() error {
+	err := b.err
+	b.err = nil
+	return err
+}
+
+func (b *BufioReader) Read(p []byte) (n int, err error) {
+	n = len(p)
+	if n == 0 {
+		return 0, b.readErr()
+	}
+	if b.r == b.w {
+		if b.err != nil {
+			return 0, b.readErr()
+		}
+		if len(p) >= len(b.buf) {
+			// Large read, empty buffer.
+			// Read directly into p to avoid copy.
+			n, b.err = b.rd.Read(p)
+			if n < 0 {
+				panic(errNegativeRead)
+			}
+			return n, b.readErr()
+		}
+		// One read.
+		// Do not use b.fill, which will loop.
+		b.r = 0
+		b.w = 0
+		n, b.err = b.rd.Read(b.buf)
+		if n < 0 {
+			panic(errNegativeRead)
+		}
+		if n == 0 {
+			return 0, b.readErr()
+		}
+		b.w += n
+	}
+
+	// copy as much as we can
+	n = copy(p, b.buf[b.r:b.w])
+	b.r += n
+	return n, nil
+}
+
+func (b *BufioReader) ReadSlice(delim byte) (line []byte, err error) {
+	for {
+		// Search buffer.
+		if i := bytes.IndexByte(b.buf[b.r:b.w], delim); i >= 0 {
+			line = b.buf[b.r : b.r+i+1]
+			b.r += i + 1
+			break
+		}
+
+		// Pending error?
+		if b.err != nil {
+			line = b.buf[b.r:b.w]
+			b.r = b.w
+			err = b.readErr()
+			break
+		}
+
+		// Buffer full?
+		if b.Buffered() >= len(b.buf) {
+			b.r = b.w
+			line = b.buf
+			err = bufio.ErrBufferFull
+			break
+		}
+
+		b.fill() // buffer is not full
+	}
+
+	return
+}
+
+func (b *BufioReader) ReadLine() (line []byte, isPrefix bool, err error) {
+	line, err = b.ReadSlice('\n')
+	if err == bufio.ErrBufferFull {
+		// Handle the case where "\r\n" straddles the buffer.
+		if len(line) > 0 && line[len(line)-1] == '\r' {
+			// Put the '\r' back on buf and drop it from line.
+			// Let the next call to ReadLine check for "\r\n".
+			if b.r == 0 {
+				// should be unreachable
+				panic("bufio: tried to rewind past start of buffer")
+			}
+			b.r--
+			line = line[:len(line)-1]
+		}
+		return line, true, nil
+	}
+
+	if len(line) == 0 {
+		if err != nil {
+			line = nil
+		}
+		return
+	}
+	err = nil
+
+	if line[len(line)-1] == '\n' {
+		drop := 1
+		if len(line) > 1 && line[len(line)-2] == '\r' {
+			drop = 2
+		}
+		line = line[:len(line)-drop]
+	}
+	return
+}
+
+func (b *BufioReader) ReadN(n int) ([]byte, error) {
+	b.grow(n)
+	for b.Buffered() < n {
+		// Pending error?
+		if b.err != nil {
+			buf := b.buf[b.r:b.w]
+			b.r = b.w
+			return buf, b.readErr()
+		}
+
+		// Buffer is full?
+		if b.Buffered() >= len(b.buf) {
+			b.r = b.w
+			return b.buf, bufio.ErrBufferFull
+		}
+
+		b.fill()
+	}
+
+	buf := b.buf[b.r : b.r+n]
+	b.r += n
+	return buf, nil
+}
+
+func (b *BufioReader) grow(n int) {
+	// Slide existing data to beginning.
+	if b.r > 0 {
+		copy(b.buf, b.buf[b.r:b.w])
+		b.w -= b.r
+		b.r = 0
+	}
+
+	// Extend buffer if needed.
+	if d := n - len(b.buf); d > 0 {
+		b.buf = append(b.buf, make([]byte, d)...)
+	}
+}
diff --git a/internal/proto/reader.go b/internal/proto/reader.go
index 8c28c7b7..70fef5e0 100644
--- a/internal/proto/reader.go
+++ b/internal/proto/reader.go
@@ -32,14 +32,12 @@ func (e RedisError) Error() string { return string(e) }
 type MultiBulkParse func(*Reader, int64) (interface{}, error)
 
 type Reader struct {
-	src *bufio.Reader
-	buf []byte
+	src *BufioReader
 }
 
-func NewReader(rd io.Reader) *Reader {
+func NewReader(src *BufioReader) *Reader {
 	return &Reader{
-		src: bufio.NewReader(rd),
-		buf: make([]byte, 4096),
+		src: src,
 	}
 }
 
@@ -47,21 +45,12 @@ func (r *Reader) Reset(rd io.Reader) {
 	r.src.Reset(rd)
 }
 
-func (r *Reader) PeekBuffered() []byte {
-	if n := r.src.Buffered(); n != 0 {
-		b, _ := r.src.Peek(n)
-		return b
-	}
-	return nil
+func (r *Reader) Bytes() []byte {
+	return r.src.Bytes()
 }
 
 func (r *Reader) ReadN(n int) ([]byte, error) {
-	b, err := readN(r.src, r.buf, n)
-	if err != nil {
-		return nil, err
-	}
-	r.buf = b
-	return b, nil
+	return r.src.ReadN(n)
 }
 
 func (r *Reader) ReadLine() ([]byte, error) {
@@ -262,38 +251,6 @@ func (r *Reader) ReadUint() (uint64, error) {
 	return util.ParseUint(b, 10, 64)
 }
 
-// --------------------------------------------------------------------
-
-func readN(r io.Reader, b []byte, n int) ([]byte, error) {
-	if n == 0 && b == nil {
-		return make([]byte, 0), nil
-	}
-
-	if cap(b) >= n {
-		b = b[:n]
-		_, err := io.ReadFull(r, b)
-		return b, err
-	}
-	b = b[:cap(b)]
-
-	pos := 0
-	for pos < n {
-		diff := n - len(b)
-		if diff > bytesAllocLimit {
-			diff = bytesAllocLimit
-		}
-		b = append(b, make([]byte, diff)...)
-
-		nn, err := io.ReadFull(r, b[pos:])
-		if err != nil {
-			return nil, err
-		}
-		pos += nn
-	}
-
-	return b, nil
-}
-
 func isNilReply(b []byte) bool {
 	return len(b) == 3 &&
 		(b[0] == StringReply || b[0] == ArrayReply) &&
diff --git a/internal/proto/reader_test.go b/internal/proto/reader_test.go
index 8d2d71be..c36e42fe 100644
--- a/internal/proto/reader_test.go
+++ b/internal/proto/reader_test.go
@@ -11,27 +11,31 @@ import (
 	. "github.com/onsi/gomega"
 )
 
+func newReader(s string) *proto.Reader {
+	return proto.NewReader(proto.NewBufioReader(strings.NewReader(s)))
+}
+
 var _ = Describe("Reader", func() {
 
 	It("should read n bytes", func() {
-		data, err := proto.NewReader(strings.NewReader("ABCDEFGHIJKLMNO")).ReadN(10)
+		data, err := newReader("ABCDEFGHIJKLMNO").ReadN(10)
 		Expect(err).NotTo(HaveOccurred())
 		Expect(len(data)).To(Equal(10))
 		Expect(string(data)).To(Equal("ABCDEFGHIJ"))
 
-		data, err = proto.NewReader(strings.NewReader(strings.Repeat("x", 8192))).ReadN(6000)
+		data, err = newReader(strings.Repeat("x", 8192)).ReadN(6000)
 		Expect(err).NotTo(HaveOccurred())
 		Expect(len(data)).To(Equal(6000))
 	})
 
 	It("should read lines", func() {
-		p := proto.NewReader(strings.NewReader("$5\r\nhello\r\n"))
+		r := newReader("$5\r\nhello\r\n")
 
-		data, err := p.ReadLine()
+		data, err := r.ReadLine()
 		Expect(err).NotTo(HaveOccurred())
 		Expect(string(data)).To(Equal("$5"))
 
-		data, err = p.ReadLine()
+		data, err = r.ReadLine()
 		Expect(err).NotTo(HaveOccurred())
 		Expect(string(data)).To(Equal("hello"))
 	})
@@ -63,7 +67,7 @@ func benchmarkParseReply(b *testing.B, reply string, m proto.MultiBulkParse, wan
 	for i := 0; i < b.N; i++ {
 		buf.WriteString(reply)
 	}
-	p := proto.NewReader(buf)
+	p := proto.NewReader(proto.NewBufioReader(buf))
 	b.ResetTimer()
 
 	for i := 0; i < b.N; i++ {
diff --git a/internal/proto/write_buffer.go b/internal/proto/write_buffer.go
index 664f4c33..51c5480b 100644
--- a/internal/proto/write_buffer.go
+++ b/internal/proto/write_buffer.go
@@ -7,23 +7,50 @@ import (
 )
 
 type WriteBuffer struct {
-	b []byte
+	rb  *BufioReader
+	buf []byte
 }
 
-func NewWriteBuffer() *WriteBuffer {
+func NewWriteBuffer(rb *BufioReader) *WriteBuffer {
 	return &WriteBuffer{
-		b: make([]byte, 0, 4096),
+		rb: rb,
 	}
 }
 
-func (w *WriteBuffer) Len() int      { return len(w.b) }
-func (w *WriteBuffer) Bytes() []byte { return w.b }
-func (w *WriteBuffer) Reset()        { w.b = w.b[:0] }
+func (w *WriteBuffer) Len() int {
+	return len(w.buf)
+}
+
+func (w *WriteBuffer) Bytes() []byte {
+	return w.buf
+}
+
+func (w *WriteBuffer) AllocBuffer() {
+	w.rb = nil
+	w.buf = make([]byte, defaultBufSize)
+}
+
+func (w *WriteBuffer) Reset() {
+	if w.rb != nil {
+		w.buf = w.rb.Buffer()[:0]
+	} else {
+		w.buf = w.buf[:0]
+	}
+}
+
+func (w *WriteBuffer) Flush() []byte {
+	b := w.buf
+	if w.rb != nil {
+		w.rb.ResetBuffer(w.buf[:cap(w.buf)])
+		w.buf = nil
+	}
+	return b
+}
 
 func (w *WriteBuffer) Append(args []interface{}) error {
-	w.b = append(w.b, ArrayReply)
-	w.b = strconv.AppendUint(w.b, uint64(len(args)), 10)
-	w.b = append(w.b, '\r', '\n')
+	w.buf = append(w.buf, ArrayReply)
+	w.buf = strconv.AppendUint(w.buf, uint64(len(args)), 10)
+	w.buf = append(w.buf, '\r', '\n')
 
 	for _, arg := range args {
 		if err := w.append(arg); err != nil {
@@ -85,19 +112,19 @@ func (w *WriteBuffer) append(val interface{}) error {
 }
 
 func (w *WriteBuffer) AppendString(s string) {
-	w.b = append(w.b, StringReply)
-	w.b = strconv.AppendUint(w.b, uint64(len(s)), 10)
-	w.b = append(w.b, '\r', '\n')
-	w.b = append(w.b, s...)
-	w.b = append(w.b, '\r', '\n')
+	w.buf = append(w.buf, StringReply)
+	w.buf = strconv.AppendUint(w.buf, uint64(len(s)), 10)
+	w.buf = append(w.buf, '\r', '\n')
+	w.buf = append(w.buf, s...)
+	w.buf = append(w.buf, '\r', '\n')
 }
 
 func (w *WriteBuffer) AppendBytes(p []byte) {
-	w.b = append(w.b, StringReply)
-	w.b = strconv.AppendUint(w.b, uint64(len(p)), 10)
-	w.b = append(w.b, '\r', '\n')
-	w.b = append(w.b, p...)
-	w.b = append(w.b, '\r', '\n')
+	w.buf = append(w.buf, StringReply)
+	w.buf = strconv.AppendUint(w.buf, uint64(len(p)), 10)
+	w.buf = append(w.buf, '\r', '\n')
+	w.buf = append(w.buf, p...)
+	w.buf = append(w.buf, '\r', '\n')
 }
 
 func formatInt(n int64) string {
diff --git a/internal/proto/write_buffer_test.go b/internal/proto/write_buffer_test.go
index 84799ff3..dba8be6d 100644
--- a/internal/proto/write_buffer_test.go
+++ b/internal/proto/write_buffer_test.go
@@ -1,6 +1,7 @@
 package proto_test
 
 import (
+	"strings"
 	"testing"
 	"time"
 
@@ -14,7 +15,7 @@ var _ = Describe("WriteBuffer", func() {
 	var buf *proto.WriteBuffer
 
 	BeforeEach(func() {
-		buf = proto.NewWriteBuffer()
+		buf = proto.NewWriteBuffer(proto.NewBufioReader(strings.NewReader("")))
 	})
 
 	It("should reset", func() {
@@ -53,7 +54,7 @@ var _ = Describe("WriteBuffer", func() {
 })
 
 func BenchmarkWriteBuffer_Append(b *testing.B) {
-	buf := proto.NewWriteBuffer()
+	buf := proto.NewWriteBuffer(proto.NewBufioReader(strings.NewReader("")))
 	args := []interface{}{"hello", "world", "foo", "bar"}
 
 	for i := 0; i < b.N; i++ {
diff --git a/pubsub.go b/pubsub.go
index f0fcb8a2..0289265b 100644
--- a/pubsub.go
+++ b/pubsub.go
@@ -46,7 +46,7 @@ func (c *PubSub) conn() (*pool.Conn, error) {
 	return cn, err
 }
 
-func (c *PubSub) _conn(channels []string) (*pool.Conn, error) {
+func (c *PubSub) _conn(newChannels []string) (*pool.Conn, error) {
 	if c.closed {
 		return nil, pool.ErrClosed
 	}
@@ -55,10 +55,14 @@ func (c *PubSub) _conn(channels []string) (*pool.Conn, error) {
 		return c.cn, nil
 	}
 
+	channels := mapKeys(c.channels)
+	channels = append(channels, newChannels...)
+
 	cn, err := c.newConn(channels)
 	if err != nil {
 		return nil, err
 	}
+	cn.WB.AllocBuffer()
 
 	if err := c.resubscribe(cn); err != nil {
 		_ = c.closeConn(cn)
@@ -69,20 +73,23 @@ func (c *PubSub) _conn(channels []string) (*pool.Conn, error) {
 	return cn, nil
 }
 
+func (c *PubSub) writeCmd(cn *pool.Conn, cmd Cmder) error {
+	cn.SetWriteTimeout(c.opt.WriteTimeout)
+	return writeCmd(cn, cmd)
+}
+
 func (c *PubSub) resubscribe(cn *pool.Conn) error {
 	var firstErr error
 
 	if len(c.channels) > 0 {
-		channels := mapKeys(c.channels)
-		err := c._subscribe(cn, "subscribe", channels...)
+		err := c._subscribe(cn, "subscribe", mapKeys(c.channels))
 		if err != nil && firstErr == nil {
 			firstErr = err
 		}
 	}
 
 	if len(c.patterns) > 0 {
-		patterns := mapKeys(c.patterns)
-		err := c._subscribe(cn, "psubscribe", patterns...)
+		err := c._subscribe(cn, "psubscribe", mapKeys(c.patterns))
 		if err != nil && firstErr == nil {
 			firstErr = err
 		}
@@ -101,16 +108,16 @@ func mapKeys(m map[string]struct{}) []string {
 	return s
 }
 
-func (c *PubSub) _subscribe(cn *pool.Conn, redisCmd string, channels ...string) error {
-	args := make([]interface{}, 1+len(channels))
-	args[0] = redisCmd
-	for i, channel := range channels {
-		args[1+i] = channel
+func (c *PubSub) _subscribe(
+	cn *pool.Conn, redisCmd string, channels []string,
+) error {
+	args := make([]interface{}, 0, 1+len(channels))
+	args = append(args, redisCmd)
+	for _, channel := range channels {
+		args = append(args, channel)
 	}
 	cmd := NewSliceCmd(args...)
-
-	cn.SetWriteTimeout(c.opt.WriteTimeout)
-	return writeCmd(cn, cmd)
+	return c.writeCmd(cn, cmd)
 }
 
 func (c *PubSub) releaseConn(cn *pool.Conn, err error, allowTimeout bool) {
@@ -166,8 +173,8 @@ func (c *PubSub) Subscribe(channels ...string) error {
 	if c.channels == nil {
 		c.channels = make(map[string]struct{})
 	}
-	for _, channel := range channels {
-		c.channels[channel] = struct{}{}
+	for _, s := range channels {
+		c.channels[s] = struct{}{}
 	}
 	return err
 }
@@ -182,8 +189,8 @@ func (c *PubSub) PSubscribe(patterns ...string) error {
 	if c.patterns == nil {
 		c.patterns = make(map[string]struct{})
 	}
-	for _, pattern := range patterns {
-		c.patterns[pattern] = struct{}{}
+	for _, s := range patterns {
+		c.patterns[s] = struct{}{}
 	}
 	return err
 }
@@ -194,10 +201,10 @@ func (c *PubSub) Unsubscribe(channels ...string) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	err := c.subscribe("unsubscribe", channels...)
 	for _, channel := range channels {
 		delete(c.channels, channel)
 	}
+	err := c.subscribe("unsubscribe", channels...)
 	return err
 }
 
@@ -207,10 +214,10 @@ func (c *PubSub) PUnsubscribe(patterns ...string) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	err := c.subscribe("punsubscribe", patterns...)
 	for _, pattern := range patterns {
 		delete(c.patterns, pattern)
 	}
+	err := c.subscribe("punsubscribe", patterns...)
 	return err
 }
 
@@ -220,7 +227,7 @@ func (c *PubSub) subscribe(redisCmd string, channels ...string) error {
 		return err
 	}
 
-	err = c._subscribe(cn, redisCmd, channels...)
+	err = c._subscribe(cn, redisCmd, channels)
 	c._releaseConn(cn, err, false)
 	return err
 }
@@ -237,8 +244,7 @@ func (c *PubSub) Ping(payload ...string) error {
 		return err
 	}
 
-	cn.SetWriteTimeout(c.opt.WriteTimeout)
-	err = writeCmd(cn, cmd)
+	err = c.writeCmd(cn, cmd)
 	c.releaseConn(cn, err, false)
 	return err
 }
diff --git a/pubsub_test.go b/pubsub_test.go
index 059b4a60..5f1fb543 100644
--- a/pubsub_test.go
+++ b/pubsub_test.go
@@ -404,4 +404,33 @@ var _ = Describe("PubSub", func() {
 		Expect(msg.Channel).To(Equal("mychannel"))
 		Expect(msg.Payload).To(Equal(string(bigVal)))
 	})
+
+	It("supports concurrent Ping and Receive", func() {
+		const N = 100
+
+		pubsub := client.Subscribe("mychannel")
+		defer pubsub.Close()
+
+		done := make(chan struct{})
+		go func() {
+			defer GinkgoRecover()
+
+			for i := 0; i < N; i++ {
+				_, err := pubsub.ReceiveTimeout(5 * time.Second)
+				Expect(err).NotTo(HaveOccurred())
+			}
+			close(done)
+		}()
+
+		for i := 0; i < N; i++ {
+			err := pubsub.Ping()
+			Expect(err).NotTo(HaveOccurred())
+		}
+
+		select {
+		case <-done:
+		case <-time.After(30 * time.Second):
+			Fail("timeout")
+		}
+	})
 })