title: What perf_counter really does
body: <p>Reading the documentation (Python 3.4) about <code>timeit.default_time()</code> it says:</p>
  
  <blockquote>
    <p>The default timer, which is always time.perf_counter().</p>
  </blockquote>
  
  <p>but reading the older documentation (Python 2.7) it says:</p>
  
  <blockquote>
    <p>Define a default timer, in a platform-specific manner. On Windows, time.clock() has microsecond granularity, but time.time()‘s granularity is 1/60th of a second. On Unix, time.clock() has 1/100th of a second granularity, and time.time() is much more precise. </p>
  </blockquote>
  
  <p>So, does <code>perf_counter()</code> simply do a choice to keep portability? I mean if the system is windows it returns <code>time.clock()</code>, otherwise <code>time.time()</code>, so that the precision grades defined above still maintain true, isn't it?</p>
  
  <p>In short, how does <code>perf_counter()</code> work?</p>