Have taken a program that calls internally the javascript engine, traced all its calls, and built a program that does all of them. i.e. built a program whose task is to make only a long list of javascript engine invokations.

Compiled and run it with java7, and did the same with java8.

This is the result:

>java -version
java version "1.7.0_60-ea"
Java(TM) SE Runtime Environment (build 1.7.0_60-ea-b04)
Java HotSpot(TM) Client VM (build 24.60-b07, mixed mode, sharing)

>java Jtest5
operations: 17176 time 2397


>java -version
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b128)
Java HotSpot(TM) Client VM (build 25.0-b69, mixed mode)

>java Jtest5
operations: 17176 time 12498

Both executions performs the same number of javascript engine invokations with the same contents, but the one using nashorn takes more than 5 times the time of the other.

Oracle cannot deploy an engine that is so much slower than the previous one.

Priority justification:
Impact: High, performance degradation
Likelhood: Medium, javascript engine invokations
Workaround: Medium, unknown

ILW = HMM => P2