CSE 120CSE 120Principles of OperatingPrinciples of OperatingSystemsSystemsWinter 2007Winter 2007Final ReviewFinal ReviewKeith Keith Marzullo Marzullo and Geoffrey M. Voelkerand Geoffrey M. VoelkerMarch 14, 2007 CSE 120 – Final Review 2 © 2007 Keith Marzullo and Geoffrey M. VoelkerCourse PlugsCourse Plugs If you like CSE 120 topics, you might find some other coursesinteresting CSE 125: Software System Design and Implementation◆ Sp05 (Voelker)◆ One project the entire quarter» Distributed, real-time, multiplayer 3D game» It might not seem like it, but it is not really a games course◆ Groups of six, oriented towards graduating seniors◆ See CSE 125 class page on Geoff's home page for details CSE 127: Introduction to Computer Security.◆ Sp05 (Savage)◆ Formal models of security as well as the bits and bytes ofsecurity exploitsMarch 14, 2007 CSE 120 – Final Review 3 © 2007 Keith Marzullo and Geoffrey M. VoelkerOverviewOverview Final mechanics Memory management Paging Page replacement Disk I/O File systems Advanced topics The EndMarch 14, 2007 CSE 120 – Final Review 4 © 2007 Keith Marzullo and Geoffrey M. VoelkerFinal MechanicsFinal Mechanics Bulk of the final covers material after midterm◆ Memory management, file systems, advanced topics Some material on concurrency, synchronization◆ Synch primitives, synch problems Based upon lecture material, homeworks, and project◆ I will use at least one question from this review on the exam Closed book, one 8.5”x11” sheet of notes◆ Yes, just one◆ Sample final on class web site Again, please, do not cheatMarch 14, 2007 CSE 120 – Final Review 5 © 2007 Keith Marzullo and Geoffrey M. VoelkerMemory ManagementMemory Management Why is memory management useful?◆ Why do we have virtual memory if it is so complex? What are the mechanisms for implementing MM?◆ Physical and virtual addressing◆ Partitioning, paging, and segmentation◆ Page tables, TLB What are the policies related to MM?◆ Page replacement What are the overheads related to providing memorymanagement?March 14, 2007 CSE 120 – Final Review 6 © 2007 Keith Marzullo and Geoffrey M. VoelkerVirtualizing Virtualizing MemoryMemory What is the difference between a physical and virtualaddress? What is the difference between fixed and variablepartitioning?◆ How do base and limit registers work? What is internal fragmentation? What is external fragmentation? What is a protection fault?March 14, 2007 CSE 120 – Final Review 7 © 2007 Keith Marzullo and Geoffrey M. VoelkerPagingPaging How is paging different from partitioning? What are the advantages/disadvantages of paging? What are page tables? What are page table entries (PTE)? Know these terms◆ Virtual page number (VPN), page frame number (PFN), offset Know how to break down virtual addresses into pagenumbers, offset How have you implemented paging in Nachos?March 14, 2007 CSE 120 – Final Review 8 © 2007 Keith Marzullo and Geoffrey M. VoelkerPage Table EntriesPage Table Entries What is a page table entry? In Nachos? What are all of the PTE bits used for?◆ Modify◆ Reference◆ Valid◆ ProtectionMarch 14, 2007 CSE 120 – Final Review 9 © 2007 Keith Marzullo and Geoffrey M. VoelkerSegmentationSegmentation What is segmentation? How does it compare/contrast with paging? What are its advantages/disadvantages with respect topartitioning, paging? What is a segment table? How can paging and segmentation be combined?March 14, 2007 CSE 120 – Final Review 10 © 2007 Keith Marzullo and Geoffrey M. VoelkerPage TablesPage Tables Page tables introduce overhead◆ Space for storing them◆ Time to use them for translation What techniques can be used to reduce theiroverhead? How do two-level (multi-level) page tables work?March 14, 2007 CSE 120 – Final Review 11 © 2007 Keith Marzullo and Geoffrey M. VoelkerTLBsTLBs What problem does the TLB solve? How do TLBs work? Why are TLBs effective? How are TLBs managed?◆ What happens on a TLB miss fault? What is the difference between a hardware andsoftware managed TLB?March 14, 2007 CSE 120 – Final Review 12 © 2007 Keith Marzullo and Geoffrey M. VoelkerPage FaultsPage Faults What is a page fault? How is it used to implement demand paged virtualmemory? What is the complete sequence of steps, from a TLBmiss to paging in from disk, for translating a virtualaddress to a physical address?◆ What is done in hardware, what is done in software?March 14, 2007 CSE 120 – Final Review 13 © 2007 Keith Marzullo and Geoffrey M. VoelkerAdvanced Advanced Mem Mem ManagementManagement What is shared memory? What is copy on write? What are memory mapped files?March 14, 2007 CSE 120 – Final Review 14 © 2007 Keith Marzullo and Geoffrey M. VoelkerPage ReplacementPage Replacement What is the purpose of the page replacementalgorithm? What application behavior does page replacement tryto exploit? When is the page replacement algorithm used? Understand◆ Belady’s (optimal), FIFO, LRU, Approximate LRU, LRU Clock,Working Set, Page Fault Frequency What is thrashing?March 14, 2007 CSE 120 – Final Review 15 © 2007 Keith Marzullo and Geoffrey M. VoelkerDiskDisk Understand the memory hierarchy concept, locality Physical disk structure◆ Platters, surfaces, tracks, sectors, cylinders, arms, heads Disk interface◆ How does the OS make requests to the disk? Disk performance◆ What steps determine disk request performance?◆ What are seek, rotation, transfer?March 14, 2007 CSE 120 – Final Review 16 © 2007 Keith Marzullo and Geoffrey M. VoelkerDisk SchedulingDisk Scheduling How can disk scheduling improve performance? What are the issues in disk scheduling?◆ Response time, throughput, fairness Review◆ FCFS, SSTF, SCAN, C-SCANMarch 14, 2007 CSE 120 – Final Review 17 © 2007 Keith Marzullo and Geoffrey M. VoelkerFile SystemsFile Systems Topics◆ Files◆ Directories◆ Sharing◆ Protection◆ Layouts◆ Buffer Cache What is a file system? Why are file systems useful (why do we have them)?March 14, 2007 CSE 120 – Final Review 18 © 2007 Keith Marzullo and Geoffrey M. VoelkerFiles and DirectoriesFiles and Directories What is a file?◆ What operations are supported?◆ What characteristics do they have?◆ What are file access methods? What is a directory?◆
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