Class Note for CMPSCI 377 at UMass(7)
Class Note for CMPSCI 377 at UMass(7)
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This 3 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Massachusetts taught by a professor in Fall. Since its upload, it has received 13 views.
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Date Created: 02/06/15
CMPSCI 377 Operating Systems Spring 2009 Lecture 1 January 27 Lecturer Mark Corner Scribes Bruno Silva Gene Novark Jim Partan 11 General information This class is taught by Prof Mark Corner in CMPSCI 142 every Monday and Wednesday from 1115am to 1230pm For additional information related to the course syllabus projects etc please visit wwwcsumasseduchornerl Although the class name is Operating Systems this course will deal mostly with largescale computer systems The main question to be studied is how to build correct reliable and high performance computer systems In order to answer this question problems such as memory management concurrency scheduling etc will be studied 111 Getting help Prof Corner has office hours on Tuesdays from 130pm to 230pm and on Thursdays from 1pm to 2pm in his office CSSSO The TA s office hours are Mondays and Fridays 1pm to 2pm in the Edlab LGRT 2325 In addition to office hours Discussion Sections will be led by the TA on Wednesdays from 125pm to 215pm in ELAB 304 ELAB is the older brick building next to the computer science building Attendance is very important since sample test problems will be discussed and the main concepts presented during the last couple of classes will be reinforced Also students looking for help can access the courses newsgroup look for the link at Prof Corner7s website Lecture notes will also be available Although this class requires no textbook interested students might look for classics of the area such as Operating System Concepts Silberschatz et all 7th Edition 112 Grading Student7s grades will depend both on exams 2 exams 25 of the final grade each and on projects Prof Corner adopts a very strict late policy so please keep that in mind when deciding when to start working on your assignments There will be four projects the first one will be worth 5 of the overall grade and the last three will each be worth 15 of the overall grade Except for the first project all the others will be done in groups Students will have 3 bonus submissions per project and a total of 3 late days across all projects The grading of all projects will be performed by an autograder system so you will have the chance to assess how well you re doing several days before the due date Do not Cheat An automatic system for nding cheaters will be used and you will be caught 11 12 Lecture 1 January 27 12 Introduction to Operating Systems The term Operating System OS is often misused It is common for example for people to speak of an OS when they are in fact referring to an OS and to a set of additional applications eg on Windows Notepad Windows Explorer etc The traditional View of the area however de nes an OS in a different way The OS can be seen as the layer and interface that stands between the userlevel applications and the hardware Its main goal is to hide the complexity of the hardware from the applications The important concept here is abstraction an OS abstracts architectural details giving programs the illusion of existing in a homogeneous environment The OS effectively makes programs believe that they live in a reliable machine with large amounts of memory a dedicated processor and so on It is also the OS s function to manage the computers resources eg the OS decides which process to runs when for how long etci 121 A Brief History of Operating Systems Operating Systems have evolved tremendously in the last few decades The rst approach for building Operating Systems taken during the 40s through early 60s was to allow only one use and one task at a timer Users had to wait for a task to be nished before they could specify another task or even interact with the computer In other words not only were OS7s monouser and monotask there was no overlapping between computation and lOi The next step in the development of OS s was to allow batch processing Now multiple jobs could be executed in a batch mode such that a program was loaded executed output was generated and then the cycle restarted with the next job Although in this type of processing there was still no interference or communication between programs some type of protection from poorly or maliciously written programs for instance was clearly needed Allowing overlap between 10 and computation was the next obvious problem to be addressed Of course this new feature brought with itself a series of new challenges such as the need for buffers interrupt handling etci Although the OS s from this time allowed users to interact with the computer while jobs were being processed only one task at a time was permitted Multiprogramming solved this and it was a task of Operating System to manage the interactions between the programs eigi which jobs to run at each time how to protect a program s memory from others etc All these were complex issues that effectively led to OS failures in the old days Eventually this additional complexity began to require that OS s be designed in a scienti c manneri During the 70s hardware became cheap but humans operators users were expensivei During this decade interaction was done via terminals in which a user could send commands to a mainframe This was the Unix erai Response time and thrashing became problems to be dealt with OS7s started to treat programs and data in a more homogeneous wayi During the 80s hardware became even cheaper It was then that PCs became widespread and very simple OSls such as DOS and the original Mac OS were used DOS for example was so simple that it didn t have any multiprogramming features From the 90s on until today hardware became even cheaper Processing demands keep increasing since then and real OSls such as Windows NT Mac OS X and Linux nally became available for PCs Operating systems are now used in a wide range of systems from cell phones and car controller computers to huge distributed systems such as Google Lecture 1 January 27 13 Computer technology has advanced 9 orders of magnitude in terms of speed size price in the last 50 years Moorels law also seems to be running out of steam mainly due to fundamental physics limits Though details are dif cult to predict we can make some guesses on what to expect in the next few years a continuing shift to multiple cores and processors serious powerheat constraints trading off computer power for reliability dealing with unreliable memory a continuing growth of large distributed systems etc Operating systems and systems software will need to continue to evolve to work with these types of systems 122 More on the focus of this course Again this course will focus more on building largescale computer systems rather than on traditional operating systems We will focus on what is needed to build systems software which is reliable fast and scalable at a layer above the traditional operating system kernel Some of the topics we will cover include o On each computer C and C providing access to details such as pointers and more concurrency and scheduling memory management and locality disks network and lesystems o Across each cluster 7 server architectures 7 distributed computing and lesystems
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