Require Rails gems one by one

require_and_profile.rb

# require_and_profile.rb
# from http://stackoverflow.com/questions/13065408/how-to-measure-how-much-memory-each-gem-requires-at-initialization
def require_and_profile(gemname = nil)
  unless gemname
    puts "%-20s: %10s | %10s" % ['gem','increment','total']
    return
  end
  #puts "Trying #{gemname}"
  # This is how to get memory of calling process in OS X, check host OS for variants
  memory_usage = `ps -o rss= -p #{Process.pid}`.to_i / 1024.0
  require gemname
  puts "%-20s: %10.2f | %10.2f" % [ gemname, (`ps -o rss= -p #{Process.pid}`.to_i / 1024.0 - memory_usage), (`ps -o rss= -p #{Process.pid}`.to_i / 1024.0)]
end

pattern = /^[^#]*gem[ ]*['"]([^,'"]*)['"][ ,~>0-9\.'"]*(:?require[: => ]*['"]([^'"]*)['"][, ]?)?/

require_and_profile
File.open('Gemfile').each do |line|
  if line.match(pattern)
  if line.match(pattern)[3]
    require_and_profile line.match(pattern)[3]
  else
      require_and_profile line.match(pattern)[1]
    end
  end
end