profiling output from Commons:Featured_picture_candidates/Log/October_2013
Patch awaiting review at gerrit change 90769
$title->getPageLanguage() gets called a lot (sometimes in the thousands of calls). Usually for the same page. This calls a hook, which can be somewhat expensive. There should be an in-process cache for it.
In particular, for https://commons.wikimedia.org/wiki/Commons:Featured_picture_candidates/Log/October_2013 we have the following profiling lines:
22.42% 12.819275 5118 - hook: PageContentLanguage
20.58% 11.766860 5118 - PageTranslationHooks::onPageContentLanguage
There may be more things that can be optimized for that page perhaps. I included some profiling data as an attachment.