erb_rendering_benchmarks.rb

require 'rubygems'
gem 'actionpack', '2.1.0'
gem 'activesupport', '2.1.0'

Kernel.module_eval do
  alias :old_require :require
  def require(file)
    old_require(file) unless file == 'html/document'
  end
end

require 'erb'
require 'active_support'
require 'action_view'
require 'benchmark'

TEMPLATE = "<b><%= name %></b> in <%= city %>, <%= state_id %>"
TEMPLATE_LAMBDA = lambda { |opt| "<b>#{opt[:name]}</b> in #{opt[:city]}, #{opt[:state_id]}" }
LOCALS = { :name => 'Wes', :city => 'Seattle', :state_id => 'WA' }

def render_with_action_view
  ActionView::Base.new.render(
    :inline => TEMPLATE,
    :layout => false,
    :locals => LOCALS
  )
end

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

def render_with_lambda
  TEMPLATE_LAMBDA.call(LOCALS)
end
times = 10000

Benchmark.bm do |bm|
  bm.report("ERB rendering using ActionView") do
    times.times { render_with_action_view }
  end

  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

  bm.report("Using a lambda") do
    times.times { render_with_lambda }
  end
end

Results

[VM] ~/dev/web/wpn_rails/test(bug_32965)$ ruby erb_rendering_benchmarks.rb 
      user     system      total        real
ERB rendering using ActionView  0.680000   0.150000   0.830000 (  0.836579)
ERB rendering using just ERB with no class cache  3.290000   0.220000   3.510000 (  3.504252)
ERB rendering using just ERB and a class cache  1.800000   0.200000   2.000000 (  2.008031)
Using a lambda  0.020000   0.020000   0.040000 (  0.045059)