erb_benchmark.rb

require 'erb'
require 'benchmark'

TEMPLATE = "<b><%= name %></b> in <%= city %>, <%= state_id %>"
LOCALS = { :name => 'Wes', :city => 'Seattle', :state_id => 'WA' }

def render_with_plain_erb
  local_variables = Struct.new(*LOCALS.keys).new(*LOCALS.values)
  ERB.new(TEMPLATE).result(local_variables.instance_eval { binding })
end

LOCAL_VARIABLE_CLASS_CACHE = Hash.new { |h, k| h[k] = Struct.new(*k) }
def render_with_plain_erb_and_class_caching
  local_variables = LOCAL_VARIABLE_CLASS_CACHE[LOCALS.keys].new(*LOCALS.values)
  ERB.new(TEMPLATE).result(local_variables.instance_eval { binding })
end

times = 100000

Benchmark.bm do |bm|
  bm.report("ERB rendering using just ERB with no class cache") do
    times.times { render_with_plain_erb }
  end

  bm.report("ERB rendering using just ERB and a class cache") do
    times.times { render_with_plain_erb_and_class_caching }
  end
end

results

ruby-1.8.7-p299 ➜  vcr git:(master) ✗ ruby benchmarks/erb_rendering.rb
      user     system      total        real
ERB rendering using just ERB with no class cache 19.230000   0.030000  19.260000 ( 19.266035)
ERB rendering using just ERB and a class cache 13.910000   0.000000  13.910000 ( 13.927047)