Describe the bug
Envoy has a severe memory leak on build master-20181004-09-15 when under load. Both the ingressgateway instances and the sidecars showed a continuously increase on memory usage during the regression patrol run, up to the point of using almost 100% of the memory available in the worker node and causing failures.

Expected behavior
No memory leaks.

Steps to reproduce the bug
Install this build and drive load to it.

Version
./istioctl version
version.BuildInfo{Version:"master-20181004-09-15", GitRevision:"24657b44315e8c0a9a53bfe5a0418984db938e7c", User:"root", Host:"72a127890223", GolangVersion:"go1.10.4", DockerHub:"gcr.io/istio-release", BuildStatus:"Clean"}

kubectl version
Client Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.8", GitCommit:"c138b85178156011dc934c2c9f4837476876fb07", GitTreeState:"clean", BuildDate:"2018-05-21T19:01:12Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.10+IKS", GitCommit:"a2e40acbc885ea18f6b745559928362c690ce062", GitTreeState:"clean", BuildDate:"2018-09-28T04:07:24Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}

Installation
Using the istio-demo.yaml from the build.

Environment
IKS

Cluster state
Plenty of data available in the regression patrol report for the run:
https://ibmcloud-perf.istio.io/regpatrol/master-20181004-09-15/istio_full