title: System V Unix and swap area
body: <p>So, I have had some problem with understanding when I started to learn mechanism of virtual memory in Unix System. So, there is <code>structure proc</code> that contains comprehensive information about any process in a system (<em>I deem that <code>proc</code> has been replaced to <code>tusk_struct</code>,but conception is actually today)</em>. <code>struct proc</code> consists address that directs to <code>struct as</code> that directs to list of <code>struct seg</code>.<a href="https://i.stack.imgur.com/ecsn2.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ecsn2.jpg" alt="enter image description here"></a></p>
  
  <p><em>Sorry for my draft!</em> Roughly it looks like on the picture. So, my answer affects virtual memory. There is <code>segvn_data</code> that is linked with <code>vnode</code>. <code>vnode</code> composes part of File System and take it upon itself of any work with file, including changing on a hard drive. Is that right that one of segment can process such pages that is mapped by <code>vnode</code>? Why should they both use <code>swap area</code>? What is responsible <code>swap area</code>?</p>
  
  <p>PS: when does segment need to change swap area?</p>
  
  <p>PPS: all processes do need to have swap area? When vnode requires that segment    maps in swap area?</p>