The author asserts that JRuby would consume more than 15GB of memory without providing any justification. Perhaps it would be better to actually try it rather than just making sweeping generalizations.
Here's a case study showing over 500k connections to a Java instance in 2.5GB of memory using NIO. JRuby's implementation of Ruby's IO is implemented directly atop NIO. So yeah...that 15GB assertion is nonsense.
http://urbanairship.com/blog/2010/08/24/c500k-in-action-at-u...