title: Probing for filesystem block size
body: <p>I'm going to first admit that this is for a class project, since it will be pretty obvious.  We are supposed to do reads to probe for the block size of the filesystem.  My problem is that the time taken to do this appears to be linearly increasing, with no steps like I would expect.</p>
  
  <p>I am timing the read like this:</p>
  
  <pre><code>double startTime = getticks();
  read = fread(x, 1, toRead, fp);
  double endTime = getticks();
  </code></pre>
  
  <p>where getticks uses rdtsc instructions.  I am afraid there is caching/prefetching that is causing the reads to not take time during the fread.  I tried creating a random file between each execution my program, but that is not alleviating my problem.</p>
  
  <p>What is the best way to accurately measure the time taken for a read from disk?  I am pretty sure my block size is 4096, but how can I get data to support that?</p>