Use one channel per packet list

libraries/networking/src/udt/PacketQueue.cpp

@@ -11,12 +11,10 @@
 
 #include "PacketQueue.h"
 
-#include "Packet.h"
 #include "PacketList.h"
 
 using namespace udt;
 
-
 MessageNumber PacketQueue::getNextMessageNumber() {
     static const MessageNumber MAX_MESSAGE_NUMBER = MessageNumber(1) << MESSAGE_NUMBER_BITS;
     _currentMessageNumber = (_currentMessageNumber + 1) % MAX_MESSAGE_NUMBER;
@@ -25,28 +23,50 @@ MessageNumber PacketQueue::getNextMessageNumber() {
 
 bool PacketQueue::isEmpty() const {
     LockGuard locker(_packetsLock);
-    return _packets.empty();
+    // Only the main channel and it is empty
+    return (_channels.size() == 1) && _channels.front().empty();
 }
 
 PacketQueue::PacketPointer PacketQueue::takePacket() {
     LockGuard locker(_packetsLock);
-    if (!_packets.empty()) {
+    if (isEmpty()) {
-        auto packet = std::move(_packets.front());
+        return PacketPointer();
-        _packets.pop_front();
-        return std::move(packet);
     }
     
-    return PacketPointer();
+    // Find next non empty channel
+    if (_channels[nextIndex()].empty()) {
+        nextIndex();
+    }
+    auto& channel = _channels[_currentIndex];
+    Q_ASSERT(!channel.empty());
+    
+    // Take front packet
+    auto packet = std::move(channel.front());
+    channel.pop_front();
+    
+    // Remove now empty channel (Don't remove the main channel)
+    if (channel.empty() && _currentIndex != 0) {
+        channel.swap(_channels.back());
+        _channels.pop_back();
+        --_currentIndex;
+    }
+    
+    return std::move(packet);
+}
+
+unsigned int PacketQueue::nextIndex() {
+    _currentIndex = ++_currentIndex % _channels.size();
+    return _currentIndex;
 }
 
 void PacketQueue::queuePacket(PacketPointer packet) {
     LockGuard locker(_packetsLock);
-    _packets.push_back(std::move(packet));
+    _channels.front().push_back(std::move(packet));
 }
 
 void PacketQueue::queuePacketList(PacketListPointer packetList) {
     packetList->preparePackets(getNextMessageNumber());
     
     LockGuard locker(_packetsLock);
-    _packets.splice(_packets.end(), packetList->_packets);
+    _channels.push_back(std::move(packetList->_packets));
-}
+}

libraries/networking/src/udt/PacketQueue.h

@@ -13,12 +13,14 @@
 #define hifi_PacketQueue_h
 
 #include <list>
+#include <vector>
 #include <memory>
 #include <mutex>
 
+#include "Packet.h"
+
 namespace udt {
     
-class Packet;
 class PacketList;
     
 using MessageNumber = uint32_t;
@@ -28,7 +30,8 @@ class PacketQueue {
     using LockGuard = std::lock_guard<Mutex>;
     using PacketPointer = std::unique_ptr<Packet>;
     using PacketListPointer = std::unique_ptr<PacketList>;
-    using PacketContainer = std::list<PacketPointer>;
+    using Channel = std::list<PacketPointer>;
+    using Channels = std::vector<Channel>;
     
 public:
     void queuePacket(PacketPointer packet);
@@ -37,14 +40,17 @@ public:
     bool isEmpty() const;
     PacketPointer takePacket();
     
-    MessageNumber getNextMessageNumber();
     Mutex& getLock() { return _packetsLock; }
     
 private:
+    MessageNumber getNextMessageNumber();
+    unsigned int nextIndex();
+    
     MessageNumber _currentMessageNumber { 0 };
     
-    mutable Mutex _packetsLock; // Protects the packets to be sent list.
+    mutable Mutex _packetsLock; // Protects the packets to be sent.
-    PacketContainer _packets; // List of packets to be sent
+    Channels _channels { 1 }; // One channel per packet list
+    unsigned int _currentIndex { 0 };
 };
 
 }

libraries/networking/src/udt/SendQueue.cpp

@@ -296,6 +296,7 @@ bool SendQueue::maybeSendNewPacket() {
             
             // grab the first packet we will send
             std::unique_ptr<Packet> firstPacket = _packets.takePacket();
+            Q_ASSERT(firstPacket);
             
             std::unique_ptr<Packet> secondPacket;
             bool shouldSendPairTail = false;