MRI does GC runs like they're going out of style. I recently did some comparisons with JRuby and saw 100x more GC runs on MRI, and easily 10x more time doing those runs. GC::Profiler ends up eating a crapload of memory as a result.

Check out slide 37 and surrounding slides. If you're complaining about GC and aren't giving JRuby a shot, you're missing out. http://www.slideshare.net/CharlesNutter/why-jruby-rubyconf-2...