code.rb

module MA; end
module MB; end
module MC; end
module MD; end
module ME; end

class A; end

class B < A
  include MA
  include MB
  include MC
  include MD
  include ME
end

class C < B; end
class D < C; end

require 'benchmark'

class A
  100_000.times do |i|
    define_method "a#{i}" do
      1
    end
  end
end

$d = D.new
$a = A.new

eval "def send_a\n #{100_000.times.map { |i| "$a.a#{i}\n" }.join} end"
eval "def send_d\n #{100_000.times.map { |i| "$d.a#{i}\n" }.join} end"

GC.disable
Benchmark.bm do |x|
  x.report("flat ") { send_a }
  x.report("deep ") { send_d }

  x.report("flat2") { send_a }
  x.report("deep2") { send_d }
end

ruby-2.0.0.txt

~/crap/ssaffronbench 2.0.0-p247 λ ruby x.rb
       user     system      total        real
flat   0.030000   0.000000   0.030000 (  0.024657)
deep   0.030000   0.000000   0.030000 (  0.029719)
flat2  0.010000   0.000000   0.010000 (  0.015495)
deep2  0.020000   0.000000   0.020000 (  0.015226)
~/crap/ssaffronbench 2.0.0-p247 λ ruby x.rb
       user     system      total        real
flat   0.030000   0.000000   0.030000 (  0.024831)
deep   0.030000   0.000000   0.030000 (  0.029739)
flat2  0.010000   0.000000   0.010000 (  0.015438)
deep2  0.020000   0.000000   0.020000 (  0.015434)
~/crap/ssaffronbench 2.0.0-p247 λ ruby x.rb
       user     system      total        real
flat   0.020000   0.000000   0.020000 (  0.023261)
deep   0.030000   0.000000   0.030000 (  0.028004)
flat2  0.020000   0.000000   0.020000 (  0.014744)
deep2  0.010000   0.000000   0.010000 (  0.014675)

ruby-2.1.0.txt

~/crap/ssaffronbench ruby-2.1.0 λ ruby x.rb
       user     system      total        real
flat   0.030000   0.000000   0.030000 (  0.027147)
deep   0.040000   0.000000   0.040000 (  0.036408)
flat2  0.010000   0.000000   0.010000 (  0.015233)
deep2  0.020000   0.000000   0.020000 (  0.014806)
~/crap/ssaffronbench ruby-2.1.0 λ ruby x.rb
       user     system      total        real
flat   0.030000   0.000000   0.030000 (  0.030373)
deep   0.040000   0.000000   0.040000 (  0.035366)
flat2  0.020000   0.000000   0.020000 (  0.015790)
deep2  0.010000   0.000000   0.010000 (  0.015687)
~/crap/ssaffronbench ruby-2.1.0 λ ruby x.rb
       user     system      total        real
flat   0.030000   0.000000   0.030000 (  0.029211)
deep   0.040000   0.000000   0.040000 (  0.037345)
flat2  0.010000   0.000000   0.010000 (  0.015964)
deep2  0.020000   0.000000   0.020000 (  0.015936)