Fast way to profile a Ruby program

simple_ruby_profile.rb

# In your code, right at the top of any source code file.
trap 'PROF' do
  File.open("/tmp/profile-#{Time.current.to_f}", 'w') {|f| f.write caller(2).join("\n") }
  pid = $$
  Thread.new { sleep 0.5; `kill -PROF #{pid}` }
end

# in a terminal
while true; do
  sleep 0.1
  kill -PROF {pid_of_your_code_running}
done

# In an irb session:
profile = Dir["/tmp/profile*"].map {|f| File.read(f).lines.first.split(/:in/).first }.reduce(Hash.new {|h,k| h[k] = 0 }) {|h, line| h[line] = h[line] + 1; h }.sort_by(&:last)

Or to analyze memory usage:

ObjectSpace.each_object.reduce(Hash.new {|h,k| h[k] = 0 }) {|all, object| all[object.class] += 1; all }