ES eating all memory despite JVM startup configuration

Elastic Stack Elasticsearch
7

i am using
openjdk version "1.8.0_31"
OpenJDK Runtime Environment (build 1.8.0_31-b13)
OpenJDK 64-Bit Server VM (build 25.31-b07, mixed mode)

w.r.t "disable the Java 7 default G1 collector if you run Elasticsearch on Java 7 later than 7u4" at http://jprante.github.io/2012/11/28/Elasticsearch-Java-Virtual-Machine-settings-explained.html

My java process has -XX:+DisableExplicitGC