It's "gone" in the sense that it's not available for other useful stuff. It is and this is the thing that people -- even software engineers -- usually misunder

It's "gone" in the sense that it's not available for other useful stuff. It is and this is the thing that people -- even software engineers -- usually misunderstand. Evicting cached data is for all intents and purposes a zero cost operation. That's why modern operating systems cache aggressively when they're not busy doing anything else: there's really no downside. If I'm caching file xyz.dll, and it turns out xyz.dll isn't needed, it's not like I have to write it back to disk or do any other (significant) work to evict it from the cache. So yes: that memory is available, at no additional cost, for any reasonable definition of "available" and "no additional cost." Honestly, why do so many just assume that the core OS kernel devs at multiple zillion-dollar companies get this fundamental Operating Systems 101 thing so spectacularly wrong in modern OSs?