message: tperf autotune parameter
  Summary: As in title.
diff: @@ -37,7 +37,8 @@ DEFINE_uint64(
  4096,
  "Amount of data written to stream each iteration");
  DEFINE_uint64(writes_per_loop, 5, "Amount of socket writes per event loop");
  -DEFINE_uint64(window, 64 * 1024, "Flow control window size");
  +DEFINE_uint64(window, 1024 * 1024, "Flow control window size");
  +DEFINE_bool(autotune_window, true, "Automatically increase the receive window");
  DEFINE_string(congestion, "newreno", "newreno/cubic/bbr/ccp/none");
  DEFINE_string(ccp_config, "", "Additional args to pass to ccp");
  DEFINE_bool(pacing, false, "Enable pacing");
  @@ -578,6 +579,7 @@ class TPerfClient : public quic::QuicSocket::ConnectionSetupCallback,
  std::chrono::milliseconds transportTimerResolution,
  int32_t duration,
  uint64_t window,
  + bool autotuneWindow,
  bool gso,
  quic::CongestionControlType congestionControlType,
  uint32_t maxReceivePacketSize)
  @@ -586,6 +588,7 @@ class TPerfClient : public quic::QuicSocket::ConnectionSetupCallback,
  eventBase_(transportTimerResolution),
  duration_(duration),
  window_(window),
  + autotuneWindow_(autotuneWindow),
  gso_(gso),
  congestionControlType_(congestionControlType),
  maxReceivePacketSize_(maxReceivePacketSize) {
  @@ -715,11 +718,10 @@ class TPerfClient : public quic::QuicSocket::ConnectionSetupCallback,
  quicClient_->setCongestionControllerFactory(
  std::make_shared<DefaultCongestionControllerFactory>());
  auto settings = quicClient_->getTransportSettings();
  - settings.advertisedInitialUniStreamWindowSize = window_;
  - // TODO figure out what actually to do with conn flow control and not sent
  - // limit.
  - settings.advertisedInitialConnectionWindowSize =
  + settings.advertisedInitialUniStreamWindowSize =
  std::numeric_limits<uint32_t>::max();
  + settings.advertisedInitialConnectionWindowSize = window_;
  + settings.autotuneReceiveConnFlowControl = autotuneWindow_;
  settings.connectUDP = true;
  settings.shouldRecvBatch = true;
  settings.shouldUseRecvmmsgForBatchRecv = true;
  @@ -771,6 +773,7 @@ class TPerfClient : public quic::QuicSocket::ConnectionSetupCallback,
  1024 * 1024 * 1024};
  std::chrono::seconds duration_;
  uint64_t window_;
  + bool autotuneWindow_{false};
  bool gso_;
  quic::CongestionControlType congestionControlType_;
  uint32_t maxReceivePacketSize_;
  @@ -832,6 +835,7 @@ int main(int argc, char* argv[]) {
  std::chrono::milliseconds(FLAGS_client_transport_timer_resolution_ms),
  FLAGS_duration,
  FLAGS_window,
  + FLAGS_autotune_window,
  FLAGS_gso,
  flagsToCongestionControlType(FLAGS_congestion),
  FLAGS_max_receive_packet_size);
  