I don't think I've ever written a substantial program that didn't have
*some* sort of caching in it, to trade off space against time somewhere
where `spend the time, every time' was undesirable. Often these caches are
not expected to be terribly large, and have the exciting expiration policy
`never', but it would be fairly trivial to respond to a mem_notify signal
by just ditching the entire contents of all of those caches.