At Phusion we run a simple multithreaded HTTP proxy server written in Ruby (which serves our DEB and RPM packages). I've seen it consume 1.3 GB of memory. This is insane – the server is stateless and doesn't do all that much! Q: What's this? A: a Ruby process's memory usage over time! Turns out I'm not alone in experiencing this issue. Ruby apps can use a lot of memory. But why? According to Herok