This is a performance bug. I have an experiment where I'm using Red Queues for web downloads. In the experiment I have idle times between resource downloads on the order of seconds. If I crank up the link rates and reduce the latency, the Estimator in the Red Queue spins for a long time trying to compute the average queue size during the idle time.

Here is the patch, instead of using a while loop, use the pow function:

--- a/src/network/utils/red-queue.cc	Fri Feb 05 01:35:39 2016 +0000
+++ b/src/network/utils/red-queue.cc	Wed Feb 10 13:07:15 2016 +0000
@@ -421,14 +421,8 @@
 RedQueue::Estimator (uint32_t nQueued, uint32_t m, double qAvg, double qW)
 {
   NS_LOG_FUNCTION (this << nQueued << m << qAvg << qW);
-  double newAve;
-
-  newAve = qAvg;
-  while (--m >= 1)
-    {
-      newAve *= 1.0 - qW;
-    }
-  newAve *= 1.0 - qW;
+  double newAve = qAvg * pow(1.0-qW, m);
+  
   newAve += qW * nQueued;
 
   // implement adaptive RED