title: Shared memory and performance
body: <p>What is the performance penalty when accessing a data structure if this is located:</p>
  
  <ul>
  <li>In the same process memory block.</li>
  <li>In a shared memory block (including locking, but supposing
  no other processes access it for a significant amount of time).</li>
  </ul>
  
  <p>I am interested in an approximate comparison values (e.g. percentage), for access, read and write.</p>