title: Purging numpy.memmap
body: <p>Given a <code>numpy.memmap</code> object created with <code>mode='r'</code> (i.e. read-only), is there a way to force it to purge all loaded pages out of physical RAM, without deleting the object itself?</p>
  
  <p>In other words, I'd like the reference to the <code>memmap</code> instance to remain valid, but all physical memory that's being used to cache the on-disk data to be uncommitted. Any views onto to the <code>memmap</code> array must also remain valid.</p>
  
  <p>I am hoping to use this as a diagnostic tool, to help separate "real" memory requirements of a script from "transient" requirements induced by the use of <code>memmap</code>.</p>
  
  <p>I'm using Python 2.7 on RedHat.</p>