Those aren't interesting questions tbh. Obviously most of the time the page cache grows to use all memory, that's the whole point of having it (using all memory that is not committed to applications as a disk cache). Overcommit obviously doesn't create memory pressure because it only exhausts address space, not memory (physical memory + swap). The relevant question is how the system behaves if it needs to allocate pages but can't find any clean (just throw'em out) or unused pages. Linux, and to a lesser degree, Windows start to thrash heavily in these scenarios. I've never seen e.g. Firefox unload a tab when this happens, regardless of OS.