celluloid-blocking.rb

require 'celluloid'

class Cell
  include Celluloid

  def expensive
    puts "[Started]"
    puts thread_count
    10000000.times { 1 + 1 }
    puts thread_count
    puts "[Finished]"
  end

  def thread_count
    Thread.list.select {|thread| thread.status == "run"}.count
  end
end

cell = Cell.new
3.times.map do
  cell.async.expensive
end

sleep