measure how fast gem require is.

require_speedtest.rb

require 'benchmark'
include Benchmark

def with_require
  fork { require 'rake' }
end

def without_require
  fork {}
end

# just a sanity check
def with_require_nofork
  require 'rake'
end

n = 200
puts "how fast is require?"
Benchmark.benchmark(CAPTION, 7, FORMAT, "require:") do |x|
  wr  = x.report("with:")    { for i in 1..n; with_require; end }
  wor = x.report("without:") { for i in 1..n; without_require; end }
  [wr-wor]
end

puts "in case you don't believe the above times, a sanity check"
Benchmark.benchmark(CAPTION, 15, FORMAT) do |x|
  nf  = x.report("nofork require:")  { for i in 1..n; with_require_nofork; end }
end

Output:

$ ruby -v
ruby 2.1.5p273 (2014-11-13 revision 48405) [x86_64-linux]
$ ruby require_speedtest.rb 
how fast is require?
              user     system      total        real
with:     0.030000   0.020000   0.050000 (  6.135141)
without:  0.010000   0.020000   0.030000 (  1.273201)
require:  0.020000   0.000000   0.020000 (  4.861940)
in case you don't believe the above times, a sanity check
                      user     system      total        real
nofork require:   0.030000   0.000000   0.030000 (  0.042729)