I built a web app using Ruby 1.8.6. Then used Ruby Enterprise Edition
and Passenger (and Apache) for production. Everything was good.
Then on a whim I decided to compile ruby 1.9.1 from source and point
my Passenger config to the new ruby binaries.
I fixed a couple things in the app, then I was up and running. However
when the app sits unused for a while, the next time I try to access it
takes several seconds. After this "warm up" it's nice and snappy
again, and remains that way until I leave it.