For parallel vacuum [1], we were discussing what is the best way to divide the cost among parallel workers but we didn't get many inputs apart from people who are very actively involved in patch development. I feel that we need some more inputs before we finalize anything, so starting a new thread.
Maybe a I just don't have experience in the type of system that parallel vacuum is needed for, but if there is any meaningful IO throttling which is active, then what is the point of doing the vacuum in parallel in the first place?