1 Review for Final Exam Memory management Three central questions File system I/O system Network Protection Security

2 Memory management: three central questions Where in memory is executing process? How do we allow multiple processes to share main memory? (protection) What’s an address and how is one interpreted?

3 Three central questions: depend on schemes Contiguous memory allocation Process placement Protection Address interpretation Paging Process placement Protection Address interpretation

4 Paging address interpretation: w/o TLB

5 Paging address interpretation: w/ TLB v = valid bit: entry is up-to-date

6 Other topics Page replacement algorithms MIN, OPT (optimal) RANDOM evict random page FIFO (first-in, first-out) give every page equal residency LRU (least-recently used) MRU (most-recently used) Approximate LRU in practice Thrashing

7 File systems File layout on disk Contiguous files Linked files Indexed files Free-Space Management Bitmap/bitvector Linked list

8 I/O systems Programmed I/O Polling Interrupt DMA RAIDs Bit-level/block-level striping Redundancy

9 Network, protection & security Read book and slides