Startup of Jython with JDK 9 (and server VM) appears to have regressed since JDK 8. Consider the following bench.py and execution with JDK 8 and JDK 9 (jdk-9+136)

import java.lang
c = java.lang.Class.forName("java.lang.Boolean")
print c
(exit)

$ time -p java -jar jython-standalone-2.7.0.jar bench.py
<type 'java.lang.Boolean'>
real 2.26
user 6.38
sys 0.26

$ time -p java --add-exports=java.base/sun.nio.ch=ALL-UNNAMED -jar jython-standalone-2.7.0.jar bench.py
<type 'java.lang.Boolean'>
real 2.36
user 7.53
sys 0.29

User time on this system has increased. Part of the issue seems to be the switch to G1. Another part may be increased usages of lambdas in the regex code.