At tonight's PDX WordPress Dev meetup (thanks for the pizza Digital Trends) Daniel Bachhuber had some questions about benchmarking a plugin. Benchmarking WordPress itself is easy, but it's harder to isolate a specific plugin, much less a few calls to preg_match_all() within it. The questioned SEO Auto Linker plugin does this on every page load, so any running time adds latency on every page.
Speculation from the meetup is that a PHP regex operating on post content, a blob, and looping through hundreds of links could be pretty slow. Too much caffeine today meant I had to give it a try.