I wanted to get a baseline benchmark of a module-loading page so I typed the above special page and to my surprise it's gone, showing an error message instead. I came here and searched for it, and while not finding about this topic, I found this listing blog post, and if you look at it, Special:ParserSpeed is a redlink.
So... where did it go? It's one convenient and comprehensive measurement tool. I don't want to go back to inspecting the html comments output by the parser one by one.