I'm not really sure if that's the solution for my problem and I realize
that advanced logging and profiling is not cheap. It just seems to me
that it's a common problem with rails (fast requests coming from
fragment caching etc, slow requests from complex pages with lots of db
queries) and was hoping others found a solution for it :)
If the slow requests require a lot of db queries and the db server
is on different server than rails, then you may try to run many rails
instances on different ports.