I've asked a question in stackoverflow, but I'll paste here for convenience

"We have analysed a heap dump file for our application (running on Tomcat with jruby 1.7.8).

It shows us that the retained heap size is very large (439,459,128) for the class org.jruby.RubyRegexp$RegexpCache. This is 48% of our memory usage

Looking at the source code for that file it is 3 final static object created at startup (patternCache / quotedPatternCache / preprocessedPatternCache)

This seems to be a pretty core part of JRuby. My question is, is it normal to have such a large percentage of the heap to be dedicated to this cache?
"

http://stackoverflow.com/questions/26630565/very-large-retained-heap-size-for-org-jruby-rubyregexpregexpcache-in-jruby-rail

Thanks for your help
All the best,
Ash