Determine whether memory location is in CPU cache

Question

It is possible for an operating system to determine whether a page of memory is in DRAM or in swap; for example, simply try to access it and if a page fault occurs, it wasn\'t.<

Answer 1

If you try to determine this yourself then the very act of running your program could invalidate the relevant cache lines, hence rendering your measurements useless.

This is one of those cases that mirrors the scientific principle that you cannot measure something without affecting that which you are measuring.