In the past i've found the following usefull:

Benchmark or Benchmark::Timer - made for benchmarking sections of code (i've only used the latter)

HTTP::WebTest - a web testing module set. it also looks like it does request time (no clue on how accurate)

To get a better picture of the load time. Load the page multiple times and take the average of the sequence. (This technique can be extended into load testing as well. Just add threaded http requests and run them all at once.)