protected function outputMemoryUsage()
    {
        $memory = memory_get_usage(true);

        $unit = array('B', 'KB', 'MB', 'GB', 'TB', 'PB');
        $memory = round($memory / pow(1024, ($i = floor(log($memory, 1024)))), 2) . ' ' . $unit[$i];

        $this->output('Memory usage: ' . $memory, self::OUTPUT_COMMENT);
    }