Simple memory usage counter which diffs vs the last call. Built for rails, but can work anywhere.

application.rb

# Add this to the very TOP of config/application.rb, before the first statement
require 'pp'
module OSCount
  def self.count(msg, force_count: false)
    return if ENV['RAILS_ENV'] == 'test'
    count = ObjectSpace.count_objects
    last_count = Thread.current['OSCount.last_count']
    Thread.current['OSCount.last_count'] = count
    show_count = last_count.nil?
    show_count = true if force_count
    free_rate = count[:FREE].to_f / count[:TOTAL]
    if show_count
      puts "OSCount first: #{msg} (free rate: #{free_rate.round(4)})"
      pp count
    end

    if last_count
      diff = {}
      count.each do |key, old_value|
        diff[key] = last_count.fetch(key, 0) - old_value
      end
      puts "OSCount diff: #{msg}"
      pp diff
    end
    nil
  end
end

OSCount.count('before application.rb')

application_controller.rb

# Inside of ApplicationController add this:
# class ApplicationController < ActionController::Base
  # Put this at the very top
  around_filter :debug_object_space

  def debug_object_space
    OSCount.count('before request')
    yield
    OSCount.count('after request', force_count: true)
  end
  
  # ... the rest of application controller
# end