CSE 120 Principles of Operating Systems Fall 2004 Final Review Geoffrey M Voelker Course Plugs z z If you like CSE 120 topics you might find some other courses interesting CSE 121 OS Architecture and Implementation z Wi05 Snoeren OS Implementation using Unix as a case study System projects with experimentation CSE 123A B Computer Networking 123A Wi05 Savage link layer up to internetworking IP 123B Sp05 Vahdat internetworking up to session application December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 2 1 Course Plugs 2 z 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 my home page for details December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 3 Overview z z z z z z z z Final mechanics Memory management Paging Page replacement Disk I O File systems Advanced topics The End December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 4 2 Final Mechanics z Bulk of the final covers material after midterm z Some material on concurrency synchronization z I will use at least one question from this review on the exam Closed book one 8 5 x11 sheet of notes z Synch primitives synch problems Based upon lecture material homeworks and project z Memory management file systems advanced topics Yes just one Sample final on class web site Again please do not cheat Have had some problems I would hate to see it on the final December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 5 Memory Management z Why is memory management useful z What are the mechanisms for implementing MM z Physical and virtual addressing Partitioning paging and segmentation Page tables TLB What are the policies related to MM z Why do we have virtual memory if it is so complex Page replacement What are the overheads related to providing memory management December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 6 3 Virtualizing Memory z z What is the difference between a physical and virtual address What is the difference between fixed and variable partitioning z z z How do base and limit registers work What is internal fragmentation What is external fragmentation What is a protection fault December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 7 Paging z z z z z 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 z z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 8 4 Page Table Entries z z What is a page table entry In Nachos What are all of the PTE bits used for Modify Reference Valid Protection December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 9 Segmentation z z z z z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 10 5 Page Tables z Page tables introduce overhead z z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 11 TLBs z z z z What problem does the TLB solve How do TLBs work Why are TLBs effective How are TLBs managed z What happens on a TLB miss fault What is the difference between a hardware and software managed TLB December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 12 6 Page Faults z z z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 13 Advanced Mem Management z z z What is shared memory What is copy on write What are memory mapped files December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 14 7 Page Replacement z z z z 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 z Belady s optimal FIFO LRU Approximate LRU LRU Clock Working Set Page Fault Frequency What is thrashing December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 15 Disk z z Understand the memory hierarchy concept locality Physical disk structure z Disk interface z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 16 8 Disk Scheduling z z How can disk scheduling improve performance What are the issues in disk scheduling z Response time throughput fairness Review FCFS SSTF SCAN C SCAN December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 17 File Systems z Topics z z Files Directories Sharing Protection Layouts Buffer Cache What is a file system Why are file systems useful why do we have them December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 18 9 Files and Directories z What is a file z What is a directory z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 19 Protection z z z z z 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 December 2 2004 CSE 120 Final Review 2004 Geoffrey M Voelker 20 10 File System Layouts z z What are file system layouts used for What are the general strategies z z z 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 December 2 2004 CSE 120 Final Review
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