Are there any drawbacks to using helper :all in Rails

Question

In Rails 'helper :all' makes all your helpers 'available' to all your controllers.

This is concise and convenient, but does it have any memory and/or performance implications compared to explicitly calling the helpers that each controller actually needs?

It's unclear form the docs whether using it involves 'require'ing all those files, or whether autoload is being used. I can't tell from the source in the Rails framework docs.

thanks