title: Shmem vs tmpfs vs mmap
body: <p>Does someone know how well the following 3 compare in terms of speed:</p>
  
  <ul>
  <li><p>shared memory</p></li>
  <li><p>tmpfs (/dev/shm)</p></li>
  <li><p>mmap (/dev/shm)</p></li>
  </ul>
  
  <p>Thanks!</p>