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Diffstat (limited to 'lib/server/TcpNice.cpp')
| -rw-r--r-- | lib/server/TcpNice.cpp | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/lib/server/TcpNice.cpp b/lib/server/TcpNice.cpp new file mode 100644 index 00000000..88d08bda --- /dev/null +++ b/lib/server/TcpNice.cpp @@ -0,0 +1,204 @@ +// -------------------------------------------------------------------------- +// +// File +// Name: TcpNice.cpp +// Purpose: Calculator for adaptive TCP window sizing to support +// low-priority background flows using the stochastic +// algorithm, as described in +// http://www.thlab.net/~lmassoul/p18-key.pdf +// Created: 11/02/2012 +// +// -------------------------------------------------------------------------- + +#include "Box.h" + +#include "TcpNice.h" +#include "Logging.h" +#include "BoxTime.h" + +#ifdef HAVE_NETINET_TCP_H +# include <netinet/tcp.h> +#endif + +#include "MemLeakFindOn.h" + +// -------------------------------------------------------------------------- +// +// Function +// Name: TcpNice::TcpNice() +// Purpose: Initialise state of the calculator +// Created: 11/02/2012 +// +// -------------------------------------------------------------------------- +TcpNice::TcpNice() +: mLastWindowSize(1), + mGammaPercent(100), + mAlphaStar(100), + mDeltaPercent(10) +{ } + +// -------------------------------------------------------------------------- +// +// Function +// Name: int GetNextWindowSize(int bytesChange, +// box_time_t timeElapsed, int rttEstimateMillis) +// Purpose: Calculate the next recommended window size, given the +// number of bytes sent since the previous recommendation, +// and the time elapsed. +// Created: 11/02/2012 +// +// -------------------------------------------------------------------------- +int TcpNice::GetNextWindowSize(int bytesChange, box_time_t timeElapsed, + int rttEstimateMicros) +{ + int epsilon = (mAlphaStar * 1000000) / rttEstimateMicros; + + // timeElapsed is in microseconds, so this will fail for T > 2000 seconds + int rateLastPeriod = ((uint64_t)bytesChange * 1000000 / timeElapsed); + + int rawAdjustment = epsilon + rateLastPeriod - + mRateEstimateMovingAverage[0]; + + int gammaAdjustment = (rawAdjustment * mGammaPercent) / 100; + + int newWindowSize = mLastWindowSize + gammaAdjustment; + + int newRateEstimateMovingAverage = + (((100 - mDeltaPercent) * mRateEstimateMovingAverage[1]) / 100) + + ((mDeltaPercent * rateLastPeriod) / 100); + + BOX_TRACE("TcpNice: " + "b=" << bytesChange << ", " + "T=" << timeElapsed << ", " + "rtt=" << rttEstimateMicros << ", " + "e=" << epsilon << ", " + "rb=" << rateLastPeriod << ", " + "rbhat=" << newRateEstimateMovingAverage << ", " + "raw=" << rawAdjustment << ", " + "gamma=" << gammaAdjustment << ", " + "wb=" << newWindowSize); + + mRateEstimateMovingAverage[0] = mRateEstimateMovingAverage[1]; + mRateEstimateMovingAverage[1] = newRateEstimateMovingAverage; + mLastWindowSize = newWindowSize; + + return newWindowSize; +} + +// -------------------------------------------------------------------------- +// +// Constructor +// Name: NiceSocketStream::NiceSocketStream( +// std::auto_ptr<SocketStream> apSocket) +// Purpose: Initialise state of the socket wrapper +// Created: 11/02/2012 +// +// -------------------------------------------------------------------------- + +NiceSocketStream::NiceSocketStream(std::auto_ptr<SocketStream> apSocket) +: mapSocket(apSocket), + mTcpNice(), + mBytesWrittenThisPeriod(0), + mPeriodStartTime(GetCurrentBoxTime()), + mTimeIntervalMillis(1000), + mEnabled(false) +{ } + +// -------------------------------------------------------------------------- +// +// Function +// Name: NiceSocketStream::Write(const void *pBuffer, int NBytes) +// Purpose: Writes bytes to the underlying stream, adjusting window size +// using a TcpNice calculator. +// Created: 2012/02/11 +// +// -------------------------------------------------------------------------- +void NiceSocketStream::Write(const void *pBuffer, int NBytes) +{ +#ifdef HAVE_DECL_SO_SNDBUF + if(mEnabled && mapTimer.get() && mapTimer->HasExpired()) + { + box_time_t newPeriodStart = GetCurrentBoxTime(); + box_time_t elapsed = newPeriodStart - mPeriodStartTime; + struct tcp_info info; + int socket = mapSocket->GetSocketHandle(); + int rtt = 50; // WAG + +# if defined HAVE_DECL_SOL_TCP && defined HAVE_DECL_TCP_INFO && defined HAVE_STRUCT_TCP_INFO_TCPI_RTT + socklen_t optlen = sizeof(info); + if(getsockopt(socket, SOL_TCP, TCP_INFO, &info, &optlen) == -1) + { + BOX_LOG_SYS_WARNING("getsockopt(" << socket << ", SOL_TCP, " + "TCP_INFO) failed"); + } + else if(optlen != sizeof(info)) + { + BOX_WARNING("getsockopt(" << socket << ", SOL_TCP, " + "TCP_INFO) return structure size " << optlen << ", " + "expected " << sizeof(info)); + } + else + { + rtt = info.tcpi_rtt; + } +# endif + + int newWindow = mTcpNice.GetNextWindowSize(mBytesWrittenThisPeriod, + elapsed, rtt); + + if(setsockopt(socket, SOL_SOCKET, SO_SNDBUF, &newWindow, + sizeof(newWindow)) == -1) + { + BOX_LOG_SYS_WARNING("getsockopt(" << socket << ", SOL_SOCKET, " + "SO_SNDBUF, " << newWindow << ") failed"); + } + + StopTimer(); + } + + if(mEnabled && !mapTimer.get()) + { + // Don't start the timer until we receive the first data to write, + // as diffing might take a long time and we don't want to bias + // the TcpNice algorithm by running while we don't have bulk data + // to send. + StartTimer(); + mPeriodStartTime = GetCurrentBoxTime(); + mBytesWrittenThisPeriod = 0; + } + + mBytesWrittenThisPeriod += NBytes; +#endif // HAVE_DECL_SO_SNDBUF + + mapSocket->Write(pBuffer, NBytes); +} + +// -------------------------------------------------------------------------- +// +// Function +// Name: NiceSocketStream::SetEnabled(bool enabled) +// Purpose: Update the enabled status, and if disabling, cancel the +// timer and set a sensible window size. +// Created: 2012/02/12 +// +// -------------------------------------------------------------------------- + +void NiceSocketStream::SetEnabled(bool enabled) +{ + mEnabled = enabled; + + if(!enabled) + { + StopTimer(); +#ifdef HAVE_DECL_SO_SNDBUF + int socket = mapSocket->GetSocketHandle(); + int newWindow = 1<<17; + if(setsockopt(socket, SOL_SOCKET, SO_SNDBUF, &newWindow, + sizeof(newWindow)) == -1) + { + BOX_LOG_SYS_WARNING("getsockopt(" << socket << ", SOL_SOCKET, " + "SO_SNDBUF, " << newWindow << ") failed"); + } +#endif + } +} |