How use callgrind/kcachegrind with rubyonrails

Hi, all:
I have installed callgrind/kcachegrind in my kubuntu for monitoring
the process performance of my RoR program.
But I encounter a problem as a jackaroo of callgrind/kcachegrind. How
could I monitor my ruby contoller or model files? Is there any tips?
Thanks very much!!

regards
ye

NO one have used it before? Then how could people evaluate the
bottleneck of RoR program?

http://snippets.aktagon.com/snippets/255-How-to-profile-your-Rails-and-Ruby-applications-with-ruby-prof