Sure they would. If zombie processes were everywhere, they'd put the effort in. How much space do you need to store info about a zombie process? It's probably 4

Sure they would. If zombie processes were everywhere, they'd put the effort in. How much space do you need to store info about a zombie process? It's probably 4 bytes: the exit code. I think that's all the info you get on Windows. That's the sort of thing they could do. Pack a bunch of them into one page or something perhaps? Or maybe just have 1 page each - and then it's still taking up 4KBytes rather than 64KBytes. But zombie processes aren't everywhere. Typically they exist briefly and then get cleaned up. So even if they could take up 4 bytes, nobody's bothered writing the code to make them do that, because what's the point? If they take up 64KBytes it's just not a very pressing problem.