CheapStrings - how do they work? (Original idea courtesy Charlie Somerville - https://gist.github.com/charliesome/5876753)

cheap.rb

#!/usr/bin/env ruby

N=10_000_000

module CheapString
  def `(s); s; end
end

class Stringer
  include CheapString

  def make_cheap_strings
    N.times do
      `hello hello hello!`
    end
  end

  def make_strings
    N.times do
      "hello hello hello!"
    end
  end
end

s = Stringer.new

if ARGV[0] == "cheap"
  puts "cheap"
  s.make_cheap_strings
else
  puts "expensive"
  s.make_strings
end

notes.txt

Confirm string creation counts:
  
  sudo dtrace -c "/Users/ben/.rbenv/versions/2.0.0-p0/bin/ruby cheap.rb" \
    -n 'ruby*:::string-create { @x = count(); }'

See all backtraces:

  sudo dtrace -c "/Users/ben/.rbenv/versions/2.0.0-p0/bin/ruby cheap.rb" \
    -n 'ruby*:::string-create { ustack(); }'

Too many! Try narrowing it down a bit:

  sudo dtrace -c "/Users/ben/.rbenv/versions/2.0.0-p0/bin/ruby cheap.rb" \
    -n 'ruby*:::string-create /arg0 == 555/ { @[ustack()] = count(); }'