Computer Science 322 Operating Systems Mount Holyoke College Spring 2008

Agenda

• Announcements
  • Extra office hours this week
    • tonight: 6:30-8:30 (or so)
    • sign up for slots or drop by during open slots
  • Any additional project proposals need to arrive soon!
  • Demonstrate your shells! No grades until demos are done!
• Memory management
  • Page faults
  • Page replacement algorithms
    • selecting a victim...
    • consider possibilities with a sample page reference string - the sequence of page numbers of the memory accesses by a program
    • First In First Out (FIFO)
      • select the page that has been in memory the longest
      • simple, but may produce many page faults given an unfortunate reference string
      • suffers from Belady's Anomaly - adding frames can actually increase the page fault count in a pathological case
    • Optimal (OPT)
      • replace the page that will not be referenced for the longest time into the future
      • the good news: it's optimal
      • the bad news: we can't know the future
      • but it's a standard to which we can compare
• Exam 2 Out
• No new lecture assignment as you work on the exam