ivar_hell.rb

$i = 1

class A
  def m
    instance_eval "@v_#{$i} = 1"
    $i = $i + 1
  end
end

def new_instance
  A.new.m
  nil
end

s = Time.now
1_000_000.times do |i|
  if i % 10000 == 0
    puts "(#{i}) last 10000 iteration took #{Time.now - s}s" 
    s = Time.now
    new_instance()
  else
    new_instance()
  end
end

output.txt

$ cat ivar_hell.rb 
$ ruby -v
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]
$ ruby ivar_hell.rb 
(0) last 10000 iteration took 6.136e-06s
(10000) last 10000 iteration took 0.468596995s
(20000) last 10000 iteration took 1.013960991s
(30000) last 10000 iteration took 1.340206003s
(40000) last 10000 iteration took 1.484439639s
(50000) last 10000 iteration took 1.781446295s
(60000) last 10000 iteration took 2.132031787s
(70000) last 10000 iteration took 2.505281806s
(80000) last 10000 iteration took 2.686239691s
(90000) last 10000 iteration took 3.013230595s
(100000) last 10000 iteration took 3.305966179s
(110000) last 10000 iteration took 3.574423993s
(120000) last 10000 iteration took 3.879910485s
(130000) last 10000 iteration took 4.333488317s
(140000) last 10000 iteration took 4.584951165s
(150000) last 10000 iteration took 4.932804317s
^C
$ rvm use jruby
Using /home/jsvd/.rvm/gems/jruby-9.0.5.0
$ ruby ivar_hell.rb 
(0) last 10000 iteration took 0.022s
(10000) last 10000 iteration took 6.936s
(20000) last 10000 iteration took 14.802s
(30000) last 10000 iteration took 27.517s
^C