CSE 120 Principles of Operating Systems Winter 2007 Final Review Keith Marzullo and Geoffrey M Voelker Course Plugs If you like CSE 120 topics you might find some other courses interesting 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 of security exploits March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 2 Overview Final mechanics Memory management Paging Page replacement Disk I O File systems Advanced topics The End March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 3 Final Mechanics Bulk of the final covers material after midterm Some material on concurrency synchronization I will use at least one question from this review on the exam Closed book one 8 5 x11 sheet of notes Synch primitives synch problems Based upon lecture material homeworks and project Memory management file systems advanced topics Yes just one Sample final on class web site Again please do not cheat March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 4 Memory Management Why is memory management useful 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 Why do we have virtual memory if it is so complex Page replacement What are the overheads related to providing memory management March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 5 Virtualizing Memory What is the difference between a physical and virtual address What is the difference between fixed and variable partitioning 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 2007 Keith Marzullo and Geoffrey M Voelker 6 Paging 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 page numbers offset How have you implemented paging in Nachos March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 7 Page Table Entries What is a page table entry In Nachos What are all of the PTE bits used for Modify Reference Valid Protection March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 8 Segmentation What is segmentation How does it compare contrast with paging What are its advantages disadvantages with respect to partitioning paging What is a segment table How can paging and segmentation be combined March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 9 Page Tables Page tables introduce overhead Space for storing them Time to use them for translation What techniques can be used to reduce their overhead How do two level multi level page tables work March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 10 TLBs 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 and software managed TLB March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 11 Page Faults What is a page fault How is it used to implement demand paged virtual memory What is the complete sequence of steps from a TLB miss to paging in from disk for translating a virtual address to a physical address What is done in hardware what is done in software March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 12 Advanced Mem Management What is shared memory What is copy on write What are memory mapped files March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 13 Page Replacement What is the purpose of the page replacement algorithm What application behavior does page replacement try to 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 2007 Keith Marzullo and Geoffrey M Voelker 14 Disk Understand the memory hierarchy concept locality Physical disk structure Disk interface Platters surfaces tracks sectors cylinders arms heads 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 2007 Keith Marzullo and Geoffrey M Voelker 15 Disk Scheduling How can disk scheduling improve performance What are the issues in disk scheduling Response time throughput fairness Review FCFS SSTF SCAN C SCAN March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 16 File 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 2007 Keith Marzullo and Geoffrey M Voelker 17 Files and Directories What is a file What is a directory What operations are supported What characteristics do they have What are file access methods What are they used for How are the implemented What is a directory entry How are directories used to do path name translation March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 18 Protection What is file protection used for How is it implemented What are access control lists ACLs What are capabilities What are the advantages disadvantages of each March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 19 File System Layouts What are file system layouts used for What are the general strategies Contiguous linked indexed What are the tradeoffs for those strategies How do those strategies reflect file access methods What is an inode How are inodes different from directories How are inodes and directories used to do path resolution find files March 14 2007 CSE 120 Final Review 2007 Keith Marzullo and Geoffrey M Voelker 20 File Buffer Cache What is the file buffer cache and why do operating systems use one What is the
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