Merge pull request #7532 from Atlante45/feat/delayed-decrease

Delay congestion epochs first decrease

assignment-client/src/assets/AssetServer.cpp

@@ -82,11 +82,11 @@ void AssetServer::completeSetup() {
     auto maxBandwidthFloat = maxBandwidthValue.toDouble(-1);
 
     if (maxBandwidthFloat > 0.0) {
-        const int BYTES_PER_MEGABITS = (1024 * 1024) / 8;
-        int maxBandwidth = maxBandwidthFloat * BYTES_PER_MEGABITS;
+        const int BITS_PER_MEGABITS = 1000 * 1000;
+        int maxBandwidth = maxBandwidthFloat * BITS_PER_MEGABITS;
         nodeList->setConnectionMaxBandwidth(maxBandwidth);
         qInfo() << "Set maximum bandwith per connection to" << maxBandwidthFloat << "Mb/s."
-                    " (" << maxBandwidth << "bytes/sec)";
+                    " (" << maxBandwidth << "bits/s)";
     }
 
     // get the path to the asset folder from the domain server settings

libraries/networking/src/udt/CongestionControl.cpp

@@ -19,6 +19,7 @@ using namespace udt;
 using namespace std::chrono;
 
 static const double USECS_PER_SECOND = 1000000.0;
+static const int BITS_PER_BYTE = 8;
 
 void CongestionControl::setMaxBandwidth(int maxBandwidth) {
     _maxBandwidth = maxBandwidth;
@@ -28,11 +29,11 @@ void CongestionControl::setMaxBandwidth(int maxBandwidth) {
 void CongestionControl::setPacketSendPeriod(double newSendPeriod) {
     Q_ASSERT_X(newSendPeriod >= 0, "CongestionControl::setPacketPeriod", "Can not set a negative packet send period");
 
-    auto maxBandwidth = _maxBandwidth.load();
-    if (maxBandwidth > 0) {
+    auto packetsPerSecond = (double)_maxBandwidth / (BITS_PER_BYTE * _mss);
+    if (packetsPerSecond > 0.0) {
         // anytime the packet send period is about to be increased, make sure it stays below the minimum period,
         // calculated based on the maximum desired bandwidth
-        double minPacketSendPeriod = USECS_PER_SECOND / (((double) maxBandwidth) / _mss);
+        double minPacketSendPeriod = USECS_PER_SECOND / packetsPerSecond;
         _packetSendPeriod = std::max(newSendPeriod, minPacketSendPeriod);
     } else {
         _packetSendPeriod = newSendPeriod;
@@ -145,17 +146,23 @@ void DefaultCC::onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {
     }
 
     _loss = true;
-    
+    ++_nakCount;
+
     static const double INTER_PACKET_ARRIVAL_INCREASE = 1.125;
     static const int MAX_DECREASES_PER_CONGESTION_EPOCH = 5;
 
     // check if this NAK starts a new congestion period - this will be the case if the
     // NAK received occured for a packet sent after the last decrease
     if (rangeStart > _lastDecreaseMaxSeq) {
+        _delayedDecrease = (rangeStart == rangeEnd);
 
         _lastDecreasePeriod = _packetSendPeriod;
-        
-        setPacketSendPeriod(ceil(_packetSendPeriod * INTER_PACKET_ARRIVAL_INCREASE));
+
+        if (!_delayedDecrease) {
+            setPacketSendPeriod(ceil(_packetSendPeriod * INTER_PACKET_ARRIVAL_INCREASE));
+        } else {
+            _loss = false;
+        }
 
         // use EWMA to update the average number of NAKs per congestion
         static const double NAK_EWMA_ALPHA = 0.125;
@@ -177,10 +184,12 @@ void DefaultCC::onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {
 
             _randomDecreaseThreshold = distribution(generator);
         }
-    } else if ((_decreaseCount++ < MAX_DECREASES_PER_CONGESTION_EPOCH) && ((++_nakCount % _randomDecreaseThreshold) == 0)) {
+    } else if (_delayedDecrease && _nakCount == 2) {
+        setPacketSendPeriod(ceil(_packetSendPeriod * INTER_PACKET_ARRIVAL_INCREASE));
+    } else if ((_decreaseCount++ < MAX_DECREASES_PER_CONGESTION_EPOCH) && ((_nakCount % _randomDecreaseThreshold) == 0)) {
         // there have been fewer than MAX_DECREASES_PER_CONGESTION_EPOCH AND this NAK matches the random count at which we
         // decided we would decrease the packet send period
-        
+
         setPacketSendPeriod(ceil(_packetSendPeriod * INTER_PACKET_ARRIVAL_INCREASE));
         _lastDecreaseMaxSeq = _sendCurrSeqNum;
     }

libraries/networking/src/udt/CongestionControl.h

@@ -15,7 +15,6 @@
 #include <atomic>
 #include <memory>
 #include <vector>
-#include <memory>
 
 #include <PortableHighResolutionClock.h>
 
@@ -61,7 +60,7 @@ protected:
     double _congestionWindowSize { 16.0 }; // Congestion window size, in packets
     
     int _bandwidth { 0 }; // estimated bandwidth, packets per second
-    std::atomic<int> _maxBandwidth { -1 }; // Maximum desired bandwidth, bytes per second
+    std::atomic<int> _maxBandwidth { -1 }; // Maximum desired bandwidth, bits per second
     double _maxCongestionWindowSize { 0.0 }; // maximum cwnd size, in packets
     
     int _mss { 0 }; // Maximum Packet Size, including all packet headers
@@ -124,6 +123,7 @@ private:
     int _randomDecreaseThreshold { 1 }; // random threshold on decrease by number of loss events
     int _avgNAKNum { 0 }; // average number of NAKs per congestion
     int _decreaseCount { 0 }; // number of decreases in a congestion epoch
+    bool _delayedDecrease { false };
 };
     
 }

libraries/networking/src/udt/Socket.cpp

@@ -354,7 +354,7 @@ void Socket::setCongestionControlFactory(std::unique_ptr<CongestionControlVirtua
 
 
 void Socket::setConnectionMaxBandwidth(int maxBandwidth) {
-    qInfo() << "Setting socket's maximum bandwith to" << maxBandwidth << ". ("
+    qInfo() << "Setting socket's maximum bandwith to" << maxBandwidth << "bps. ("
             << _connectionsHash.size() << "live connections)";
     _maxBandwidth = maxBandwidth;
     for (auto& pair : _connectionsHash) {

tools/udt-test/src/UDTTest.cpp

@@ -57,13 +57,13 @@ const QCommandLineOption STATS_INTERVAL {
 };
 
 const QStringList CLIENT_STATS_TABLE_HEADERS {
-    "Send (P/s)", "Est. Max (P/s)", "RTT (ms)", "CW (P)", "Period (us)",
+    "Send (Mb/s)", "Est. Max (Mb/s)", "RTT (ms)", "CW (P)", "Period (us)",
     "Recv ACK", "Procd ACK", "Recv LACK", "Recv NAK", "Recv TNAK",
     "Sent ACK2", "Sent Packets", "Re-sent Packets"
 };
 
 const QStringList SERVER_STATS_TABLE_HEADERS {
-    "  Mb/s  ", "Recv P/s", "Est. Max (P/s)", "RTT (ms)", "CW (P)",
+    "  Mb/s  ", "Recv Mb/s", "Est. Max (Mb/s)", "RTT (ms)", "CW (P)",
     "Sent ACK", "Sent LACK", "Sent NAK", "Sent TNAK",
     "Recv ACK2", "Duplicates (P)"
 };
@@ -364,7 +364,11 @@ void UDTTest::handleMessage(std::unique_ptr<Message> message) {
 void UDTTest::sampleStats() {
     static bool first = true;
     static const double USECS_PER_MSEC = 1000.0;
-    
+    static const double MEGABITS_PER_BYTE = 8.0 / 1000000.0;
+    static const double MS_PER_SECOND = 1000.0;
+    static const double PPS_TO_MBPS = 1500.0 * MEGABITS_PER_BYTE;
+
+
     if (!_target.isNull()) {
         if (first) {
             // output the headers for stats for our table
@@ -378,8 +382,8 @@ void UDTTest::sampleStats() {
         
         // setup a list of left justified values
         QStringList values {
-            QString::number(stats.sendRate).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
-            QString::number(stats.estimatedBandwith).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
+            QString::number(stats.sendRate * PPS_TO_MBPS).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
+            QString::number(stats.estimatedBandwith * PPS_TO_MBPS).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
             QString::number(stats.rtt / USECS_PER_MSEC, 'f', 2).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
             QString::number(stats.congestionWindowSize).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
             QString::number(stats.packetSendPeriod).rightJustified(CLIENT_STATS_TABLE_HEADERS[++headerIndex].size()),
@@ -408,16 +412,13 @@ void UDTTest::sampleStats() {
             
             int headerIndex = -1;
             
-            static const double MEGABITS_PER_BYTE = 8.0 / 1000000.0;
-            static const double MS_PER_SECOND = 1000.0;
-            
             double megabitsPerSecond = (stats.receivedBytes * MEGABITS_PER_BYTE * MS_PER_SECOND) / _statsInterval;
             
             // setup a list of left justified values
             QStringList values {
                 QString::number(megabitsPerSecond, 'f', 2).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
-                QString::number(stats.receiveRate).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
-                QString::number(stats.estimatedBandwith).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
+                QString::number(stats.receiveRate * PPS_TO_MBPS).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
+                QString::number(stats.estimatedBandwith * PPS_TO_MBPS).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
                 QString::number(stats.rtt / USECS_PER_MSEC, 'f', 2).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
                 QString::number(stats.congestionWindowSize).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),
                 QString::number(stats.events[udt::ConnectionStats::Stats::SentACK]).rightJustified(SERVER_STATS_TABLE_HEADERS[++headerIndex].size()),