collect do
  next if not File.readable?('/proc/meminfo')

  # calculate app memory from total
  apps = 0

  File.open('/proc/meminfo') do |file|
    file.each do |line|
      key, value, unit = line.chomp.split
      key.gsub!(/:/, '')
      value = value.to_i * 1024

      case key
      when "MemTotal"
        apps = value
      when "MemFree"
        Metriks.histogram("os.mem:unused").update(value)
        apps -= value
      when "Buffers"
        Metriks.histogram("os.mem:buffers").update(value)
        apps -= value
      when "Cached"
        Metriks.histogram("os.mem:cache").update(value)
        apps -= value
      when "SwapCached"
        Metriks.histogram("os.mem:swap_cache").update(value)
        apps -= value
      when "Slab"
        Metriks.histogram("os.mem:slab_cache").update(value)
        apps -= value
      when "PageTables"
        Metriks.histogram("os.mem:page_tables").update(value)
        apps -= value
      when "Mapped"
        Metriks.histogram("os.mem:mapped").update(value)
      end
    end

    Metriks.histogram("os.mem:apps").update(apps)
  end
end