Avoid extra calls to Smarty::getTemplateDir

[ejegg]

They end up doing lots of redundant path normalization. Make sure we only register each directory once per process, even if we are resetting the Config singleton multiple times (e.g. for locale swapping).

Overview

Stop slowdowns caused by lots of redundant calls to internal smarty functions.

Before

We noticed long-running processes with template rendering would slow down over time, to the point where rendering a single email would take 10 sec. This happened when using Smarty 3 or 5, but not with Smarty 2.

After

Long-running processes with rendering do not slow down.

Technical Details

Profiling showed most of the time in the Smarty::_realpath function, called from Smarty::_normalizeTemplateConfig. It turns out just calling getTemplateDir triggers this over and over again. We are switching locales during the long-running process to render different language emails, so the config hooks are running and re-registering template directories.

[civibot]

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[ejegg]

Oops, looks like @eileenmcnaughton already submitted a similar PR