Вы можете переопределить Kernel.require
следующим образом:
module Kernel
# make an alias of the original require
alias_method :original_require, :require
# rewrite require
def require name
start = Time.now
# code to time
ret = original_require name
finish = Time.now
diff = finish - start
# TODO: This should really add up all of
# the require calls for a certain module
if diff > 0.1
puts "#{diff} #{name}"
end
ret
end
end