Computer Science 432/563
Operating Systems

Spring 2016, The College of Saint Rose

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Agenda

• Announcements
  • Hey, no class Monday!
  • Programming Project 3: knish: The Knight Shell on to part 2 functionality
  • Term Project set your groups this week
• Lecture 0x0e assignment recap, Banker's algorithm questions
• Lecture 0x0f assignment recap
• Paging
  • another option: inverted page tables
  • memory protection with paging: valid/invalid bits
  • shared pages
• 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

No New Lecture Assignment

The problems formerly occupying this space will be due as part of the next lecture assignment.

The readings for next class are SG&G Chapter 8.