At some point you want to check that there aren’t any really slow bits of your application and even if there aren’t, you might like to know where to spend effort in optimising. Luckily for you the script/performance/request script coupled with ruby-prof gem produces very useful profiling reports.
Getting script/performance/request to work with the standard gem (version 0.6.0) is troublesome impossible, however that nice man Jeremy Kemper from 37signals has published a version (0.6.1) that does work! Hurrah!
You can just install jeremy-ruby-prof from the git gem repo, however this installs the gem with the wrong name if you want to use it with script/performance/request. It can be done by downloading the gem, building the gem and then installing it from the local gem. E.g. (on a Ubuntu box):
tar -xf jeremy-ruby-prof-89e2a4bc3f5881519a2fe1e5c5c05f7e1e0acf6e
sudo gem install pkg/ruby-prof-0.6.1.gem
Ta da! Installed with the right name and now you will be able to create yourself a benchmarking environment and profiling script like the tutorial at Railscase – Request Profiling.
By default, two outputs are generated in your tmp/ directory. An HTML call graph (see Reading Call Graphs) and a flat profile (txt) file.