Project 3 due 12 4 Lecture 17 Final Review CSE 120 Principles of Operating Systems Alex C Snoeren Course Plugs If you liked CSE 120 topics you might find some other courses interesting CSE 121 OS Architecture and Implementation Wi06 Your s truly OS Implementation using Unix as a case study System projects with experimentation CSE 123A B Computer Networking 123A Fa06 Varghese link layer up to internetworking IP 123B Sp06 Vahdat internetworking up to application 2 CSE 120 Lecture 17 Course Plugs 2 CSE 125 Software System Design and Implementation Sp06 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 Voelker s home page for details CSE 127 Intro to Computer Security Wi06 Savage Focus on security realities in a networked environment Both offense and defense 3 CSE 120 Lecture 17 Overview Final mechanics Memory management Paging Page replacement Disk I O File systems Advanced file systems Networked file systems Security The End 4 CSE 120 Lecture 17 Final Mechanics Bulk of the final covers material after midterm Some material on concurrency synchronization Likely to be questions on Nachos Closed book no notes Synch primitives synch problems Based upon lecture material homeworks and project Memory management file systems security Expect similar style to midterm just longer Again please do not cheat I want you all to graduate 5 CSE 120 Lecture 17 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 6 CSE 120 Lecture 17 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 7 CSE 120 Lecture 17 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 Know how to break down virtual addresses into page numbers offset Virtual page number VPN page frame number PFN offset I might ask you to figure out sizes of page tables offsets etc How have you implemented paging in Nachos 8 CSE 120 Lecture 17 Page Table Entries What is a page table entry In Nachos What are all of the PTE bits used for Modify Reference Valid Protection 9 CSE 120 Lecture 17 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 10 CSE 120 Lecture 17 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 11 CSE 120 Lecture 17 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 12 CSE 120 Lecture 17 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 13 CSE 120 Lecture 17 Advanced Mem Management What is shared memory What is copy on write How does it make use of the PTE bits What are memory mapped files 14 CSE 120 Lecture 17 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 Different replacement algorithms Belady s optimal FIFO LRU Approximate LRU LRU Clock Working Set Page Fault Frequency What is Belady s anomaly thrashing 15 CSE 120 Lecture 17 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 16 CSE 120 Lecture 17 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 Know why or why not these might still be important 17 CSE 120 Lecture 17 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 18 CSE 120 Lecture 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 19 CSE 120 Lecture 17 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 20 CSE 120 Lecture 17 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 21 CSE 120 Lecture 17 File Buffer Cache What is the file buffer cache and why do operating systems use one What is the difference between caching reads and caching writes What are the tradeoffs of using memory for a file buffer cache vs VM 22 CSE 120 Lecture 17 Advanced File Systems What is FFS and how is it an improvement over the original Unix file system What is LFS and how is it an improvement over FFS What is RAID and how does it help file system performance and reliability 23 CSE 120 Lecture 17 Networked File Systems What is RPC and how is it implemented What is a stub compiler Interface What is NFS how does it relate to file systems and RPC How does NFS bind clients to servers What does it mean for NFS servers to
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