@UncombedCoconut one month later, but thanks a lot for trying some numbers (in addition to fixing the issue in the first place)! I'll see if I can find the time to measure it a tiny bit more consistently (inserting a timer around the relevant parts), but your numbers suggest that #2747 isn't useful anymore (which, despite the effort I put into, I'd be happy to get rid of). Anyway, it doesn't seem like having it in slows anything down measurably, so there's no hurry -- but not remembering what it was all about.