title: FreeBSD zone allocator
body: <p>I am reading the freeBSD book authored by Marshall McKusick and George Neville-Neil. In the kernel memory management, it mentions the following about zone allocator:</p>
  
  <blockquote>
    <p>Each memory type is given its own zone from which all its allocations are made. Memory allocated in one zone cannot be used by any other zone or by the general memory allocator.</p>
  </blockquote>
  
  <p>My question is:</p>
  
  <p>1) What memory types are being referred here ?</p>
  
  <p>2) What is meant by the different zones in context of zone allocator ?</p>
  
  <p>If someone can also provide some reference that explains this better, it would be appreciated.</p>
  
  <p>Thanks.</p>