Nashorn is slower than Rhino on B-Tree test

A DESCRIPTION OF THE REQUEST :
Using the B-Tree script available at

https://github.com/ysangkok/js-clrs-btree

and running runnashorn.sh or runrhino.sh, each iteration is consistently slower in Nashorn than it is in Rhino. After disabling the calls into Java code, it is still slower.

JUSTIFICATION :
Nashorn promised improved performance over Rhino. The main rationale behind Nashorn is benefiting from JSR-292: Dynamic Languages on the JVM aka InvokeDynamic. Since Nashorn uses this technology, which Rhino does not, it should be possible to achieve superior performance. Since superior performance has not been achieved, this bug is filed.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Performance ideally as good as Rhino.
ACTUAL -
On my machine, Nashorn is consistently 1/3 slower than Rhino.