[eluser]ivantcholakov[/eluser]
2.6MB memory usage is fine. On the other hand, the name of the configuration file "autoload.php" maybe is misleading for newcomers. Everything declared there loads immediately.
CodeIgniter 3 has the minimal required version 5.2.4 for PHP. This means the SPL (standard PHP library) is always available. spl_autoload_register() and related functions will be always available. I wonder then whether it is good for CodeIgniter to provide code/a way for lazy auto-loading of classes. I have my implementation, but I restrained myself to talk about such a feature, because I wait the release. Although coding is easy, such a feature needs some discussion. Some standard is needed.