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RTT fixes (#7428)

* Few code updates

* Do not show average RTT before timing out

* Fix unwanted integer division in RTTStatistics

* Fix float format, prettier jitter calculation

* Use +=, 0.1f -> 100.0f for stronger average updates
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HybridDog authored and nerzhul committed Jun 23, 2018
1 parent 07b1743 commit 968ce9af598024ec71e9ffb2d15c3997a13ad754
Showing with 34 additions and 39 deletions.
  1. +10 −2 src/client.cpp
  2. +12 −23 src/network/connection.cpp
  3. +3 −3 src/network/connection.h
  4. +7 −10 src/network/connectionthreads.cpp
  5. +2 −1 src/network/peerhandler.h
@@ -437,7 +437,7 @@ void Client::step(float dtime)
counter = 0.0;
// connectedAndInitialized() is true, peer exists.
float avg_rtt = getRTT();
infostream << "Client: avg_rtt=" << avg_rtt << std::endl;
infostream << "Client: average rtt: " << avg_rtt << std::endl;
}

/*
@@ -1706,9 +1706,17 @@ void Client::afterContentReceived()
delete[] text;
}

// returns the Round Trip Time
// if the RTT did not become updated within 2 seconds, e.g. before timing out,
// it returns the expired time instead
float Client::getRTT()
{
return m_con->getPeerStat(PEER_ID_SERVER,con::AVG_RTT);
float avg_rtt = m_con->getPeerStat(PEER_ID_SERVER, con::AVG_RTT);
float time_from_last_rtt =
m_con->getPeerStat(PEER_ID_SERVER, con::TIMEOUT_COUNTER);
if (avg_rtt + 2.0f > time_from_last_rtt)
return avg_rtt;
return time_from_last_rtt;
}

float Client::getCurRate()
@@ -825,8 +825,9 @@ void Peer::DecUseCount()
delete this;
}

void Peer::RTTStatistics(float rtt, const std::string &profiler_id,
unsigned int num_samples) {
void Peer::RTTStatistics(float rtt, const std::string &profiler_id)
{
static const float avg_factor = 100.0f / MAX_RELIABLE_WINDOW_SIZE;

if (m_last_rtt > 0) {
/* set min max values */
@@ -837,32 +838,24 @@ void Peer::RTTStatistics(float rtt, const std::string &profiler_id,

/* do average calculation */
if (m_rtt.avg_rtt < 0.0)
m_rtt.avg_rtt = rtt;
m_rtt.avg_rtt = rtt;
else
m_rtt.avg_rtt = m_rtt.avg_rtt * (num_samples/(num_samples-1)) +
rtt * (1/num_samples);
m_rtt.avg_rtt += (rtt - m_rtt.avg_rtt) * avg_factor;

/* do jitter calculation */

//just use some neutral value at beginning
float jitter = m_rtt.jitter_min;

if (rtt > m_last_rtt)
jitter = rtt-m_last_rtt;

if (rtt <= m_last_rtt)
jitter = m_last_rtt - rtt;
float jitter = std::fabs(rtt - m_last_rtt);

if (jitter < m_rtt.jitter_min)
m_rtt.jitter_min = jitter;
if (jitter >= m_rtt.jitter_max)
m_rtt.jitter_max = jitter;

if (m_rtt.jitter_avg < 0.0)
m_rtt.jitter_avg = jitter;
m_rtt.jitter_avg = jitter;
else
m_rtt.jitter_avg = m_rtt.jitter_avg * (num_samples/(num_samples-1)) +
jitter * (1/num_samples);
m_rtt.jitter_avg += (jitter - m_rtt.jitter_avg) * avg_factor;

if (!profiler_id.empty()) {
g_profiler->graphAdd(profiler_id + "_rtt", rtt);
@@ -934,16 +927,12 @@ void UDPPeer::setNonLegacyPeer()

void UDPPeer::reportRTT(float rtt)
{
if (rtt < 0.0) {
return;
}
RTTStatistics(rtt,"rudp",MAX_RELIABLE_WINDOW_SIZE*10);
assert(rtt >= 0.0f);

RTTStatistics(rtt, "rudp");

float timeout = getStat(AVG_RTT) * RESEND_TIMEOUT_FACTOR;
if (timeout < RESEND_TIMEOUT_MIN)
timeout = RESEND_TIMEOUT_MIN;
if (timeout > RESEND_TIMEOUT_MAX)
timeout = RESEND_TIMEOUT_MAX;
timeout = rangelim(timeout, RESEND_TIMEOUT_MIN, RESEND_TIMEOUT_MAX);

MutexAutoLock usage_lock(m_exclusive_access_mutex);
resend_timeout = timeout;
@@ -593,15 +593,15 @@ class Peer {
return m_rtt.jitter_max;
case AVG_JITTER:
return m_rtt.jitter_avg;
case TIMEOUT_COUNTER:
return m_timeout_counter;
}
return -1;
}
protected:
virtual void reportRTT(float rtt) {};

void RTTStatistics(float rtt,
const std::string &profiler_id = "",
unsigned int num_samples = 1000);
void RTTStatistics(float rtt, const std::string &profiler_id = "");

bool IncUseCount();
void DecUseCount();
@@ -1167,19 +1167,16 @@ SharedBuffer<u8> ConnectionReceiveThread::handlePacketType_Control(Channel *chan

// a overflow is quite unlikely but as it'd result in major
// rtt miscalculation we handle it here
float rtt;
if (current_time > p.absolute_send_time) {
float rtt = (current_time - p.absolute_send_time) / 1000.0;

// Let peer calculate stuff according to it
// (avg_rtt and resend_timeout)
dynamic_cast<UDPPeer *>(peer)->reportRTT(rtt);
rtt = (current_time - p.absolute_send_time) / 1000.0f;
} else if (p.totaltime > 0) {
float rtt = p.totaltime;

// Let peer calculate stuff according to it
// (avg_rtt and resend_timeout)
dynamic_cast<UDPPeer *>(peer)->reportRTT(rtt);
rtt = p.totaltime;
}

// Let peer calculate stuff according to it
// (avg_rtt and resend_timeout)
dynamic_cast<UDPPeer *>(peer)->reportRTT(rtt);
}
// put bytes for max bandwidth calculation
channel->UpdateBytesSent(p.data.getSize(), 1);
@@ -30,7 +30,8 @@ typedef enum {
AVG_RTT,
MIN_JITTER,
MAX_JITTER,
AVG_JITTER
AVG_JITTER,
TIMEOUT_COUNTER
} rtt_stat_type;

class Peer;

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