CS162Operating Systems andSystems ProgrammingLecture 2History of the World Parts 1—5 Operating Systems StructuresAugust 31, 2005Prof. John Kubiatowiczhttp://inst.eecs.berkeley.edu/~cs162Lec 2.28/31/05 Kubiatowicz CS162 ©UCB Fall 2005Review: What does an Operating System do?• Silerschatz and Gavin:“An OS is Similar to a government”– Begs the question: does a government do anything useful by itself?• Coordinator and Traffic Cop:– Manages all resources– Settles conflicting requests for resources– Prevent errors and improper use of the computer• Facilitator:– Provides facilities that everyone needs– Standard Libraries, Windowing systems– Make application programming easier, faster, less error-prone• Some features reflect both tasks:– E.g. File system is needed by everyone (Facilitator)– But File system must be Protected (Traffic Cop)Lec 2.38/31/05 Kubiatowicz CS162 ©UCB Fall 2005Review: Virtual Machine Abstraction• Software Engineering Problem: – Turn hardware/software quirks ⇒what programmers want/need– Optimize for convenience, utilization, security, reliability, etc…• For Any OS area (e.g. file systems, virtual memory, networking, scheduling):– What’s the hardware interface? (physical reality)– What’s the application interface? (nicer abstraction)ApplicationOperating SystemHardwarePhysical Machine InterfaceVirtual Machine InterfaceLec 2.48/31/05 Kubiatowicz CS162 ©UCB Fall 2005Review: Example of Address TranslationProg 1VirtualAddressSpace 1Prog 2VirtualAddressSpace 2CodeDataHeapStackCodeDataHeapStackData 2Stack 1Heap 1OS heap & StacksCode 1Stack 2Data 1Heap 2Code 2OS codeOS dataTranslation Map 1 Translation Map 2Physical Address SpaceLec 2.58/31/05 Kubiatowicz CS162 ©UCB Fall 2005Review: Dual Mode Operation• Hardware provides at least two modes:– “Kernel” mode (or “supervisor” or “protected”)– “User” mode: Normal programs executed • Some instructions/ops prohibited in user mode:– Example: cannot modify page tables in user mode» Attempt to modify ⇒ Exception generated• Transitions from user mode to kernel mode:– System Calls, Interrupts, Other exceptionsLec 2.68/31/05 Kubiatowicz CS162 ©UCB Fall 2005Goals for Today• History of Operating Systems– Really a history of resource-driven choices• Operating Systems Structures• Operating Systems OrganizationsNote: Some slides and/or pictures in the following areadapted from slides ©2005 Silberschatz, Galvin, and Gagne Lec 2.78/31/05 Kubiatowicz CS162 ©UCB Fall 2005Moore’s law changeTypical academic computer 1981 vs 20050.2$4,000$25,000≤ 0.1≤ 110s23216110,0001 Gb/s9600 b/s100,0001TB10MB32,7684GB128KB3806—40 38000.25—0.5103—10 Factor20051981Price#users/machine# addr bitsNet bandwidthDisk capacityDRAM capacityCPU MHz,Cycles/instLec 2.88/31/05 Kubiatowicz CS162 ©UCB Fall 2005Dawn of timeENIAC: (1945—1955)• “The machine designed by Drs. Eckert and Mauchlywas a monstrosity. When it was finished, the ENIAC filled an entire room, weighed thirty tons, and consumed two hundred kilowatts of power.”• http://ei.cs.vt.edu/~history/ENIAC.Richey.HTMLLec 2.98/31/05 Kubiatowicz CS162 ©UCB Fall 2005History Phase 1 (1948—1970)Hardware Expensive, Humans Cheap• When computers cost millions of $’s, optimize for more efficient use of the hardware!– Lack of interaction between user and computer• User at console: one user at a time• Batch monitor: load program, run, print• Optimize to better use hardware– When user thinking at console, computer idle⇒BAD!– Feed computer batches and make users wait – Autograder for this course is similar•No protection:what if batch program has bug?Lec 2.108/31/05 Kubiatowicz CS162 ©UCB Fall 2005Core Memories (1950s & 60s)• Core Memory stored data as magnetization in iron rings– Iron “cores” woven into a 2-dimensional mesh of wires– Origin of the term “Dump Core”– Rumor that IBM consulted Life Saver company• See: http://www.columbia.edu/acis/history/core.htmlThe first magnetic core memory, from the IBM 405 Alphabetical Accounting Machine. Lec 2.118/31/05 Kubiatowicz CS162 ©UCB Fall 2005History Phase 1½ (late 60s/early 70s)• Data channels, Interrupts: overlap I/O and compute– DMA – Direct Memory Access for I/O devices– I/O can be completed asynchronously• Multiprogramming: several programs run simultaneously– Small jobs not delayed by large jobs– More overlap between I/O and CPU– Need memory protection between programs and/or OS• Complexity gets out of hand:– Multics: announced in 1963, ran in 1969» www.multicians.org lists 1777 people who “contributed to Multics”. Probably 30-40 core developers.» Turing award lecture from Fernando Corbató (key researcher): “On building systems that will fail”– OS 360: released with 1000 known bugs (APARs)» “Anomalous Program Activity Report”• OS finally becomes and important science:– How to deal with complexity???– UNIX based on Multics but vastly simplifiedLec 2.128/31/05 Kubiatowicz CS162 ©UCB Fall 2005A Multics System (Circa 1976)• The 6180 at MIT IPC, skin doors open, circa 1976:– “We usually ran the machine with doors open so the operators could see the AQ register display, which gave you an idea of the machine load, and for convenient access to the EXECUTE button, which the operator would push to enter BOS if the machine crashed.”• http://www.multicians.org/multics-stories.htmlLec 2.138/31/05 Kubiatowicz CS162 ©UCB Fall 20051973:1. 7 Mbit/sq. in140 MBytes1979:7. 7 Mbit/sq. in2,300 MBytessource: New York Times, 2/23/98, page C3, “Makers of disk drives crowd even more data into even smaller spaces”Early Disk HistoryLec 2.148/31/05 Kubiatowicz CS162 ©UCB Fall 2005History Phase 2 (1970 – 1985)Hardware Cheaper, Humans Expensive• Computers available for tens of thousands of dollars instead of millions• OS Technology maturing/stabilizing•Interactivetimesharing:– Use cheap terminals (~$1000) to let multiple users interact with the system at the same time– Sacrifice CPU time to get better response time– Users do debugging, editing, and email online• Problem: Thrashing– Performance very non-linear response with load– Thrashing caused by manyfactors including» Swapping, queueingUsersResponsetimeLec 2.158/31/05 Kubiatowicz CS162 ©UCB Fall 2005Administriva: Time for Project Signup• Project Signup:– The group signup page is now working– Only submit
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