More relevantly, swapping pages to flash storage would kill the flash storage itself. (Flash memory has terrible write endurance, and what endurance it has reli

More relevantly, swapping pages to flash storage would kill the flash storage itself. (Flash memory has terrible write endurance, and what endurance it has relies on obscure GC algorithms that would interact quite terribly with a "swap file"-like pattern!) Performance isn't actually a huge concern until you start swapping out your working set (i.e. actively threshing); even swapping to spinning rust, which has terrible performance, is better than having no swap at all! Edit: You could still swap out to "external", modular storage like an SD card, since killing that would be no big deal - just treat it as disposable. But no SD card slot on iPhones :-P