Version 1.8 of istio is due to the addition of DNS cache in the agent.Will this cause sidecar memory to be higher ？
Istio is using the coredns golang library and it has some memory statistics here. In 1.8 i believe the proxy is disabled by default so you wont have to worry about the memory yet. https://github.com/coredns/deployment/blob/42e68b15520b300af4ad20b9b96fecc469c88b01/kubernetes/Scaling_CoreDNS.md