title: stack pointer and segmentation
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/3211600/how-does-a-stack-memory-increase">How does a stack memory increase?</a>  </p>
  </blockquote>
  
  
  
  <p>let's think of an OS using segmentation.<br>
  My question is : does the os intrecepts every changes of the stack pointer<br>
  and instanly ( or quite instanly ) allocates/deallocates space in phisical memory<br>
  or it does so using a clever strategy allocating more memory than you need when you decrement the sp , deallocating memory only when freed memory has reached a certain amount ?</p>
  
  <p>I hope my quetsion is clear enough.</p>