title: Determine whether memory location is in CPU cache
body: <p>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.</p>
  
  <p>However, is the same thing possible with CPU cache? </p>
  
  <p>Is there any efficient way to tell whether a given memory location has been loaded into a cache line, or to know when it does so?</p>