send multiple packets at once, if the pacing delay is very small

This is an optimization to avoid waking of the run loop every couple of
microseconds.

internal/mocks/ackhandler/sent_packet_handler.go

@@ -153,6 +153,18 @@ func (mr *MockSentPacketHandlerMockRecorder) SetHandshakeComplete() *gomock.Call
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SetHandshakeComplete", reflect.TypeOf((*MockSentPacketHandler)(nil).SetHandshakeComplete))
 }
 
+// ShouldSendNumPackets mocks base method
+func (m *MockSentPacketHandler) ShouldSendNumPackets() int {
+	ret := m.ctrl.Call(m, "ShouldSendNumPackets")
+	ret0, _ := ret[0].(int)
+	return ret0
+}
+
+// ShouldSendNumPackets indicates an expected call of ShouldSendNumPackets
+func (mr *MockSentPacketHandlerMockRecorder) ShouldSendNumPackets() *gomock.Call {
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ShouldSendNumPackets", reflect.TypeOf((*MockSentPacketHandler)(nil).ShouldSendNumPackets))
+}
+
 // ShouldSendRetransmittablePacket mocks base method
 func (m *MockSentPacketHandler) ShouldSendRetransmittablePacket() bool {
 	ret := m.ctrl.Call(m, "ShouldSendRetransmittablePacket")

internal/protocol/server_parameters.go

@@ -131,3 +131,8 @@ const NumCachedCertificates = 128
 // 1. it reduces the framing overhead
 // 2. it reduces the head-of-line blocking, when a packet is lost
 const MinStreamFrameSize ByteCount = 128
+
+// MinPacingDelay is the minimum duration that is used for packet pacing
+// If the packet packing frequency is higher, multiple packets might be sent at once.
+// Example: For a packet pacing delay of 20 microseconds, we would send 5 packets at once, wait for 100 microseconds, and so forth.
+const MinPacingDelay time.Duration = 100 * time.Microsecond

internal/utils/minmax.go

@@ -114,6 +114,14 @@ func MinTime(a, b time.Time) time.Time {
 	return a
 }
 
+// MaxTime returns the later time
+func MaxTime(a, b time.Time) time.Time {
+	if a.After(b) {
+		return a
+	}
+	return b
+}
+
 // MaxPacketNumber returns the max packet number
 func MaxPacketNumber(a, b protocol.PacketNumber) protocol.PacketNumber {
 	if a > b {

internal/utils/minmax_test.go

@@ -49,6 +49,13 @@ var _ = Describe("Min / Max", func() {
 			Expect(MaxPacketNumber(1, 2)).To(Equal(protocol.PacketNumber(2)))
 			Expect(MaxPacketNumber(2, 1)).To(Equal(protocol.PacketNumber(2)))
 		})
+
+		It("returns the maximum time", func() {
+			a := time.Now()
+			b := a.Add(time.Second)
+			Expect(MaxTime(a, b)).To(Equal(b))
+			Expect(MaxTime(b, a)).To(Equal(b))
+		})
 	})
 
 	Context("Min", func() {