Computer Science 322 Operating Systems Mount Holyoke College Spring 2008

Agenda

• Announcements
  • No class or office hours on Friday
  • Final project proposals due Friday
  • Exam out Monday
  • Demonstrate your shells
• Exam review
• Memory Management
  • Demand paging
    • only bring in pages that are actually requested
    • when a page is referenced that is not in memory - generate a page fault
    • page fault traps to OS, bring in the page
    • allows a mechanism for virtual memory
    • if a page fault occurs and no free frame is available, we need to make one - send a frame (the victim) back to disk
    • performance will depend on the page fault rate
    • low page fault rate results in reasonably low effective access times, high page fault rates will make effective access times very high
    • locality of reference will make for a reasonably good effective access time in most circumstances