The poor man's memory profiling

memory_profiling_spec.rb

it "should use constant memory" do
  warm_up_measure = memory_usage_for_items(1)

  small_inputs_memory = memory_usage_for_items(1)
  large_inputs_memory = memory_usage_for_items(200)

  large_inputs_memory.should be <= small_inputs_memory * 1.05
end

def memory_usage_for_items(item_count)
  data = setup(item_count)
  memory_peak_of do
    process(data)
  end
end

def memory_peak_of
  peak_usage = 0
  finished = false

  initial_usage = current_living_objects
  profiler = Thread.new do
    while not finished
      peak_usage = [peak_usage, current_living_objects].max
      sleep(0.01)
    end
  end

  yield

  finished = true
  profiler.join

  peak_usage - initial_usage
end

def current_living_objects
  GC.start
  object_counts = ObjectSpace.count_objects
  object_counts[:TOTAL] - object_counts[:FREE]
end

def setup(items_count)
  ...
end

def process(data)
  ...
end