Whenever I run JRuby or JIRB using 9.0.0.0, installed with RVM, on a 64-bit Ubuntu 14.04.2 Linux 3.16.0-43 system, I get four warning lines:
jruby: warning: unknown property jruby.memory.max
jruby: warning: unknown property jruby.stack.max
jruby: warning: unknown property jruby.memory.max
jruby: warning: unknown property jruby.stack.max
It looks like those properties are hardcoded (to 500m and 2048k, respectively) in jruby-launcher-1.0.15-java/argparser.cpp now.