profile-tools

https://github.com/dougyouch/profile-tools

Profile methods without touching their code. List them in config/profile_tools.yml, restart, and every request logs how many times each was called, how long it took, exactly how many objects it allocated and how many garbage collections ran inside it. Remove the file and restart to turn it off, so it can be switched on for a production box and off again. Rails apps need no setup beyond the Gemfile; other apps can load the file or profile methods by name. Built for finding the code that creates the most objects and causes the most garbage collection.