saltstack/salt — pull request #10766 by s0undt3ch (2014-02-26 07:55:22+00:00)
Title: Reduce scaling issues with `deepcopy`'ing.

Transform `dict`, `list`, `set` into it's immutable partner which is
lazy loaded. So, if no attribute access is being performed, the
built-ins are not converted and cached into it's immutable version.

Fixes #10733.