title: Why file read is faster on reading again?
body: <p><pre><code>SIZE = 1&lt;&lt;16
  def justread(file):
      with open(file, 'rb') as f:
          while f.read(SIZE):
              pass
  </pre></code></p>
  
  <p>The first time I run this function on a 700MB file it took 19 secs.
  When I repeated<br/>
  reading the same file again the time it took dropped to 0.5secs.<br/>
  I repeated this with many files and the results were similar.<br/>
  What is going on here?</p>