From cb0801fc16b691c516ecac725224c0df66c9a348 Mon Sep 17 00:00:00 2001 From: orignal Date: Wed, 11 Sep 2024 20:54:22 -0400 Subject: [PATCH] reduce number of retransmits --- libi2pd/Streaming.cpp | 66 +++++++++++++++++++++++++------------------ libi2pd/Streaming.h | 7 +++-- 2 files changed, 43 insertions(+), 30 deletions(-) diff --git a/libi2pd/Streaming.cpp b/libi2pd/Streaming.cpp index ba71f0ac..5cabc36c 100644 --- a/libi2pd/Streaming.cpp +++ b/libi2pd/Streaming.cpp @@ -76,7 +76,7 @@ namespace stream m_IsTimeOutResend (false), m_IsImmediateAckRequested (false), m_LocalDestination (local), m_RemoteLeaseSet (remote), m_ReceiveTimer (m_Service), m_SendTimer (m_Service), m_ResendTimer (m_Service), m_AckSendTimer (m_Service), m_NumSentBytes (0), m_NumReceivedBytes (0), m_Port (port), - m_RTT (INITIAL_RTT), m_SlowRTT (INITIAL_RTT), m_WindowSize (INITIAL_WINDOW_SIZE), m_LastWindowDropSize (0), + m_RTT (INITIAL_RTT), m_SlowRTT (INITIAL_RTT), m_SlowRTT2 (INITIAL_RTT), m_WindowSize (INITIAL_WINDOW_SIZE), m_LastWindowDropSize (0), m_WindowDropTargetSize (0), m_WindowIncCounter (0), m_RTO (INITIAL_RTO), m_AckDelay (local.GetOwner ()->GetStreamingAckDelay ()), m_PrevRTTSample (INITIAL_RTT), m_Jitter (0), m_MinPacingTime (0), @@ -103,7 +103,7 @@ namespace stream m_IsResendNeeded (false), m_IsFirstRttSample (false), m_IsSendTime (true), m_IsWinDropped (false), m_IsTimeOutResend (false), m_IsImmediateAckRequested (false), m_LocalDestination (local), m_ReceiveTimer (m_Service), m_SendTimer (m_Service), m_ResendTimer (m_Service), m_AckSendTimer (m_Service), - m_NumSentBytes (0), m_NumReceivedBytes (0), m_Port (0), m_RTT (INITIAL_RTT), m_SlowRTT (INITIAL_RTT), + m_NumSentBytes (0), m_NumReceivedBytes (0), m_Port (0), m_RTT (INITIAL_RTT), m_SlowRTT (INITIAL_RTT), m_SlowRTT2 (INITIAL_RTT), m_WindowSize (INITIAL_WINDOW_SIZE), m_LastWindowDropSize (0), m_WindowDropTargetSize (0), m_WindowIncCounter (0), m_RTO (INITIAL_RTO), m_AckDelay (local.GetOwner ()->GetStreamingAckDelay ()), m_PrevRTTSample (INITIAL_RTT), m_Jitter (0), m_MinPacingTime (0), @@ -550,27 +550,34 @@ namespace stream { m_RTT = rttSample; m_SlowRTT = rttSample; + m_SlowRTT2 = rttSample; m_PrevRTTSample = rttSample; + m_Jitter = rttSample / 10; // 10% + m_Jitter += 5; // for low-latency connections m_IsFirstRttSample = false; } else - m_RTT = RTT_EWMA_ALPHA * rttSample + (1.0 - RTT_EWMA_ALPHA) * m_RTT; - // calculate jitter - double jitter = 0; - if (rttSample > m_PrevRTTSample) - jitter = rttSample - m_PrevRTTSample; - else if (rttSample < m_PrevRTTSample) - jitter = m_PrevRTTSample - rttSample; - else - jitter = std::round (rttSample / 10); // 10% - jitter += 1; // for low-latency connections - m_Jitter = (0.025 * jitter) + (1.0 - 0.025) * m_Jitter; + m_RTT = (m_PrevRTTSample + rttSample) / 2; + if (!m_IsWinDropped) + { + m_SlowRTT = SLOWRTT_EWMA_ALPHA * m_RTT + (1.0 - SLOWRTT_EWMA_ALPHA) * m_SlowRTT; + m_SlowRTT2 = RTT_EWMA_ALPHA * m_RTT + (1.0 - RTT_EWMA_ALPHA) * m_SlowRTT2; + // calculate jitter + double jitter = 0; + if (rttSample > m_PrevRTTSample) + jitter = rttSample - m_PrevRTTSample; + else if (rttSample < m_PrevRTTSample) + jitter = m_PrevRTTSample - rttSample; + else + jitter = rttSample / 10; // 10% + jitter += 5; // for low-latency connections + m_Jitter = (0.05 * jitter) + (1.0 - 0.05) * m_Jitter; + } // // delay-based CC - if ((m_RTT > m_SlowRTT + m_Jitter && rttSample > m_RTT && rttSample > m_PrevRTTSample) && !m_IsWinDropped) // Drop window if RTT grows too fast, late detection + if ((m_SlowRTT2 > m_SlowRTT + m_Jitter && rttSample > m_SlowRTT2 && rttSample > m_PrevRTTSample) && !m_IsWinDropped) // Drop window if RTT grows too fast, late detection ProcessWindowDrop (); UpdatePacingTime (); - m_SlowRTT = SLOWRTT_EWMA_ALPHA * rttSample + (1.0 - SLOWRTT_EWMA_ALPHA) * m_SlowRTT; m_PrevRTTSample = rttSample; bool wasInitial = m_RTO == INITIAL_RTO; @@ -579,18 +586,23 @@ namespace stream if (wasInitial) ScheduleResend (); } - if (ackThrough > m_DropWindowDelaySequenceNumber && m_WindowSize <= m_WindowDropTargetSize) + if (m_IsWinDropped && ackThrough > m_DropWindowDelaySequenceNumber) + { + m_IsFirstRttSample = true; m_IsWinDropped = false; - if (acknowledged && m_IsWinDropped && m_WindowSize > m_WindowDropTargetSize) + } + if (m_WindowDropTargetSize && m_WindowSize <= m_WindowDropTargetSize) { - if (ackCount > 1) - m_WindowSize = m_SentPackets.size () + 1; - else - { - m_WindowSize = m_SentPackets.size (); - m_IsResendNeeded = true; - } + m_WindowDropTargetSize = 0; + m_DropWindowDelaySequenceNumber = m_SequenceNumber; + } + if (acknowledged && m_WindowDropTargetSize && m_WindowSize > m_WindowDropTargetSize) + { + m_RTO = std::max (MIN_RTO, (int)(m_RTT * 1.5 + m_Jitter)); // we assume that the next rtt sample may be much larger than the current + m_IsResendNeeded = true; + m_WindowSize = m_SentPackets.size () + 1; // if there are no packets to resend, just send one regular packet if (m_WindowSize < MIN_WINDOW_SIZE) m_WindowSize = MIN_WINDOW_SIZE; + if (m_WindowSize > MAX_WINDOW_SIZE) m_WindowSize = MAX_WINDOW_SIZE; m_WindowIncCounter = 0; UpdatePacingTime (); } @@ -598,10 +610,10 @@ namespace stream { ScheduleResend (); } - if ((m_SendBuffer.IsEmpty () && m_SentPackets.size () > 0) // tail loss - || int(m_SentPackets.size ()) > m_WindowSize) // or we drop window + if (m_SendBuffer.IsEmpty () && m_SentPackets.size () > 0) // tail loss { m_IsResendNeeded = true; + m_RTO = std::max (MIN_RTO, (int)(m_RTT * 1.5 + m_Jitter)); // to prevent spurious retransmit } if (m_SentPackets.empty () && m_SendBuffer.IsEmpty ()) { @@ -1304,7 +1316,7 @@ namespace stream if (m_NumResendAttempts == 1 && m_RTO != INITIAL_RTO) { // loss-based CC - if (!m_IsWinDropped) + if (!m_IsWinDropped && LOSS_BASED_CONTROL_ENABLED) ProcessWindowDrop (); } else if (m_IsTimeOutResend) diff --git a/libi2pd/Streaming.h b/libi2pd/Streaming.h index 70853d64..63fe2033 100644 --- a/libi2pd/Streaming.h +++ b/libi2pd/Streaming.h @@ -56,8 +56,8 @@ namespace stream const int INITIAL_WINDOW_SIZE = 10; const int MIN_WINDOW_SIZE = 2; const int MAX_WINDOW_SIZE = 512; - const double RTT_EWMA_ALPHA = 0.25; - const double SLOWRTT_EWMA_ALPHA = 0.125; + const double RTT_EWMA_ALPHA = 0.5; + const double SLOWRTT_EWMA_ALPHA = 0.05; const double PREV_SPEED_KEEP_TIME_COEFF = 0.35; // 0.1 - 1 // how long will the window size stay around the previous drop level, less is longer const int MIN_RTO = 20; // in milliseconds const int INITIAL_RTT = 8000; // in milliseconds @@ -72,6 +72,7 @@ namespace stream const uint64_t SEND_INTERVAL = 1000; // in microseconds const uint64_t REQUEST_IMMEDIATE_ACK_INTERVAL = 7500; // in milliseconds const uint64_t REQUEST_IMMEDIATE_ACK_INTERVAL_VARIANCE = 3200; // in milliseconds + const bool LOSS_BASED_CONTROL_ENABLED = 1; // 0/1 struct Packet { @@ -282,7 +283,7 @@ namespace stream uint16_t m_Port; SendBufferQueue m_SendBuffer; - double m_RTT, m_SlowRTT; + double m_RTT, m_SlowRTT, m_SlowRTT2; float m_WindowSize, m_LastWindowDropSize, m_WindowDropTargetSize; int m_WindowIncCounter, m_RTO, m_AckDelay, m_PrevRTTSample; double m_Jitter;