I feel like part of the point of this comment went un-understood: my "I'm willing to believe" aside was meant to downplay the importance of user applications; the fact that system applications do not get randomly killed when suspended means that the low-memory notification system is actually much more expensive than "kill some processes" (which, honestly, is still quite expensive, given that the detection is done asynchronously in a different process and requires a bunch of context switches, page-table flushes, and zeroing in order to reclaim that memory).