Intellij with Scala cosumes huge memory

I have used Scala plugin in my idea IDE. I am actually developing ScalaJS project. First 10 minutes run okay without problem, then gradually, the memory consumption increases and in 30 minutes it consumes around 6 GB! In my Intellij IDE, I am running the command ~fastOptJS.

Is it normal?

I am using:

JAVA

openjdk version "1.8.0_191"
OpenJDK Runtime Environment (build 1.8.0_191-8u191-b12-2ubuntu0.18.04.1-b12)
OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)

OS

Linux mint 19 Cinnamon 64 bit

IDEA

2018.3