Final ReviewCS-502 Fall CS-502 Operating Systems Fall 2006 Review

Final ReviewCS-502 Fall Week 1 Concurrency Processes – a fundamental abstraction Interrupts, dispatching, ready queue Busy waiting, Peterson’s solution Critical sections, semaphores Processes (à la Unix, Linux, Windows) What does this include? Process states fork() and exec()

Final ReviewCS-502 Fall Week 2 Threads Concurrency within an address space Shared (virtual) memory programming Lightweight concurrency Scheduling Goals and criteria FCFS, RR, Priority, SJF, etc. Multi-level scheduling (later) Rate monotonic, Earliest Deadline First –(for real time problems)

Final ReviewCS-502 Fall Week 3 Producer-consumer models Interprocess communication Shared memory Semaphores Software interrupts & signals to processes Pipes Message passing Monitors Remote procedure call

Final ReviewCS-502 Fall Week 4 – Memory Management Partitioning physical memory Base and Limit registers The first “virtual” memory Easy relocation Segmentation Multiple segments Paging Page tables & page translation Copy-on-write & other tricks

Final ReviewCS-502 Fall Week 4 – Memory Management (cont.) Virtual Memory Page replacement algorithms Paging performance calculations Locality of reference ; thrashing Cache: Fundamental principle that cuts across all of computing Physical memory is cache of virtual memory TLB is a cache of page tables File caches, activity caches, etc. Fundamental issues in caching

Final ReviewCS-502 Fall Week 5 – I/O subsystems Types of I/O devices Character vs. block vs. graphic vs. streaming Types of transfers Programmed I/O Interrupt-driven DMA Device drivers Statically loaded vs. dynamically loaded Interrupt handling: bottom vs. top half

Final ReviewCS-502 Fall Weeks 6 & 7 – Disks and File Systems Disks I/O devices mostly used for storage within system Randomly accessed; blocks independently writeable Bad block management Disk economics Moore’s law increase in densities Slow, linear increase in performance RAID Protection against disk failures Some improvements in performance Stable storage Also protection against failures Generalizes to transaction management

Final ReviewCS-502 Fall Weeks 6 & 7 – Disks and File Systems (cont.) Disk scheduling algorithms Not particularly relevant except in some database or multimedia systems File: Fundamental abstraction of persistent storage Also used for system functions (including protection) File metadata Information about the file, stored with file Container vs. contents

Final ReviewCS-502 Fall Weeks 6 & 7 – Disks and File Systems (cont.) Operations on files Read, write, seek, create, delete, truncate, open, close, etc. Types of file allocation Contiguous Linked (or FAT) Indexed Directory A special kind of file Linux virtual file systems Mounting

Final ReviewCS-502 Fall Week 8 – Networks OSI seven-layer stack Connection A fundamental abstraction of networking Socket An OS abstraction; one end of a connection Network layer Routing Transport layer Reliable transmission

Final ReviewCS-502 Fall Week 9 – Distributed File System DFS naming & access DFS caching File server semantics Stateless vs. stateful Example systems NFS – a stateless system AFS – very much a stateful system

Final ReviewCS-502 Fall Week 10 – Multiprocessing and Distributed Systems Types of multi-computers Shared memory multiprocessors Clusters of separate computers Distributed systems SMP One operating system Multiple computations in kernel at once Processes & interrupts execute on any processor

Final ReviewCS-502 Fall Week 10 – Multiprocessing and Distributed Systems (cont.) Clusters Physically close; separate OS on each machine Shared I/O and disk devices Fast IPC & RPC Load balancing Distributed computing Physically separated; internet communications Distributed file systems; NFS, etc.

Final ReviewCS-502 Fall Week 11 – Virtualization Decoupling of hardware from {OS, appl.} Insulates systems from each other Commissioning and updates Debugging new version Separate OS required by separate applications Dynamic repartitioning of hardware Move running applications Balancing shifting loads

Final ReviewCS-502 Fall Week 11 & 12 – Multimedia Systems Delivery of audio, video, etc, streams to computers Broad impact in last decade TiVo, iPod, video on demand, audio/video on PCs CD & DVD disk and file formats Compression is essential JPEG, MPEG, MP-3 Lossless vs. lossy Take advantage of temporal locality

Final ReviewCS-502 Fall Week 11 & 12 – Multimedia Systems (cont.) Processor and disk scheduling Rate monotonic: equivalent to any static algorithm Earliest deadline first: equiv. to any dynamic alg. Multimedia file organization Frame vs. blocked; Locations on disk Network streaming Progressive download vs. real-time Real-time streaming Live vs. video-audio on demand

Final ReviewCS-502 Fall Week 13 – Protection and Security Protection Mechanisms in OS to keep processes from things they should not touch Access control lists vs. capabilities Separate policy from mechanism Security Validating credentials of users, processes Validating authenticity of messages, controls, etc. Cryptography General security mechanism Public key vs. private key methods

Final ReviewCS-502 Fall Term Projects At least 5 real-time operating systems eCos, VxWorks, QNX Neutrino, Itron, ThreadX, Nucleus Lots of embedded systems RTOS, plus Visual DSP++ Personal devices: PalmOS, Symbian Games: PSP Very small devices: TinyOS, BrickOS Big systems Telephone exchanges: Chorus Corporate computing: Open VMs Eclectic systems Inferno, Squeak

Final ReviewCS-502 Fall Other topics OS organization Big vs. small Monolithic kernel vs. microkernel Linux kernel projects Adding a system call Building a message passing subsystem Discovering answers to questions …

Final ReviewCS-502 Fall Questions