Merge pull request #13388 from y-zeng/flow_control

Flow control fixes

src/core/ext/transport/chttp2/transport/flow_control.cc

@@ -312,7 +312,9 @@ double TransportFlowControl::SmoothLogBdp(grpc_exec_ctx* exec_ctx,
   double bdp_error = value - pid_controller_.last_control_value();
   const double dt = (double)(now - last_pid_update_) * 1e-3;
   last_pid_update_ = now;
-  return pid_controller_.Update(bdp_error, dt);
+  // Limit dt to 100ms
+  const double kMaxDt = 0.1;
+  return pid_controller_.Update(bdp_error, dt > kMaxDt ? kMaxDt : dt);
 }
 
 FlowControlAction::Urgency TransportFlowControl::DeltaUrgency(

src/core/ext/transport/chttp2/transport/writing.cc

@@ -322,7 +322,7 @@ class DataSendContext {
         GPR_MIN(stream_remote_window(), t_->flow_control->remote_window()));
   }
 
-  bool AnyOutgoing() const { return max_outgoing() != 0; }
+  bool AnyOutgoing() const { return max_outgoing() > 0; }
 
   void FlushCompressedBytes() {
     uint32_t send_bytes =