CS 153 Design of Operating Systems Spring 18

Transcription

1 CS 153 Design of Operating Systems Spring 18 Lectre 1: Corse Introdction Instrctor: Chengy Song Slide contribtions from Nael Ab-Ghazaleh, Harsha Madhyvasta and Zhiyn Qian

2 Teaching Staff Chengy Song I am an Assistant Professor in CSE» 2nd year at UCR, feedback is important Office hors Tesday and Thrsday 4-5pm or by appointment» Hope to meet many of yo dring office hors Two TAs Lin Jiang and Daimeng Wang» Gradate stdents in Compter Science Office hors TBA Leads for Labs 2

3 Class Overview Check class webpage for information Will send ot link to webpage Lectre slides, homeworks, and projects will be posted on class webpage Assignment trn-in throgh ilearn Digital only, no paper copy Annoncements throgh ilearn and posted on class webpage Piazza for discssion forms; link on website Use these please Stay on top of things falling behind can snowball qickly into troble 3

4 Textbook Apraci-Dessa and Apraci-Dessa, OS, 3 easy pieces (reqired + free!) Other good books: Anderson and Dahlin, Operating Systems: Principles and Practice (recommended) Silberschatz, Galvin, and Gagne, Operating System Concepts, John Wiley and Sons, 8th Edition (recommended) 4

5 Class Overview Grading breakdown projects (40% total)» Xv6 Operating system» Book ses examples from it» 4 projects (sed to be 2, splitting into halves) To keep the TA load nder control, they will grade each two together 4 homeworks (20% total) Mid-term (16%) Final (24%) Engagement/extra credit (4%)» Incldes attendance in lab. and lectre» Yo learn mch better if yo are interested and engaged 5

6 Projects Project framework this time: xv6 Projects are in C Very good debgging spport Used in OS class at several other niversities Start to get familiar immediately We will start labs. next Friday Go over the xv6 docmentation (on the corse web page) Optional Lab 0 to help get familiar with what xv6 is 6

7 Projects are HARD! Probably the hardest class yo will take at UCR in terms of development effort Yo mst learn gdb if yo want to preserve yor sanity! J Working on the projects will take most of yor time in this class Biggest reason the projects are hard: legacy code Yo have to nderstand existing code before yo can add more code Preparation for main challenge yo will face at any real job 7

8 Project Recommendations Easier if yo are engaged/excited Find a partner that yo like/trst Do not start working on projects at last minte! A lot of the time will be spend nderstanding the code Debgging is integral process of development Make good se of help available Post qestions on piazza Take advantage of TA office hors Come prepared to Labs Again, learning to debg 8

9 Project Logistics Projects to be done in grops of two When yo have chosen grops, send yor grop info to yor TA Use the find a partner featre in piazza» if nable to find partner and we ll form grops Option to switch partners after project two First step is to conceptally nderstand the project Then come p with implementation plan» Fail and fail again» Debg, debg, debg (systems are nforgiving)» àsccess!! 9

10 Homeworks and Exams For homeworks Assigned on Wednesdays, de in one week Can expect similar qestions on the exams Midterm (tentatively May 4) In class Final (Jne 12, 7-10pm) Covers second half of class + selected material from first part» I will be explicit abot the material covered» Becase first midterm is short (50 mintes) No makep exams Unless dire circmstances 10

11 Sbmission Policies Homeworks de on ilearn by the end of the day (will be specified on ilearn) Code and design docments for projects de by the end of the day (similarly will be specified on ilearn) Late policy (also on corse webpage): 4 slack days across all deliverables» Will se the ilearn sbmission timestamp to determine the days» 2% bons point if yo dont not se any of the slack days 10% penalty for every late day beyond slack days 11

12 Recipe for SUCCESS in CS153 Start early on projects Attend labs and office hors Take advantage of available help Be engaged, interested, crios Make sre to attend lectres Going over slides is not the same Try to read textbook material before class Ask qestions when something is nclear 4% participation and extra credit may bmp p yor grade if on borderline. Face recognition J 12

13 How Not To Pass CS 153 Do not come to lectre It s nice ot, the slides are online, and the material is in the book anyway Lectre material is the basis for exams and directly relates to the projects I often see capable stdents hrt themselves badly (fail, or get miserable grades) by not attending Do not ask qestions in lectre, office hors, or It s scary, I don t want to embarrass myself Asking qestions is the best way to clarify lectre material at the time it is being presented Office hors and will help with projects 13

14 How Not To Pass (2) Wait ntil the last cople of days to start a project We ll have to do the crnch anyways, why do it early? The projects cannot be done in the last few days Repeat: The projects cannot be done in the last few days Each qarter grops learn that starting early meant finishing all of the projects on time and some do not 14

15 Objectives of this class In this corse, we will stdy problems and soltions that go into design of an OS to address these isses Focs on concepts rather than particlar OS Specific OS for examples Develop an nderstanding of how OS and hardware impacts application performance and reliability Examples: What cases yor code to crash when yo access NULL? What happens behind a printf()? Why can mlti-threaded code be slower than single-threaded code? 15

16 Qestions for today Why do we need operating systems corse? Why do we need operating systems? What does an operating system need to do? Looking back, looking forward 16

17 Why yo shold care Stdent srveys show low interest coming in Compters are an amazing feat of engineering Perhaps the greatest hman achievement Yo get to nderstand how they work OS, Architectre, Compilers, PL, are the magic that makes compters possible Ors is a yong field Or Newtons, Einsteins, LaPlace s, happened in the last centry Many of or giants are still alive So mch innovation at an nbelievable pace Yo can help write the next chapter 17

18 Why an OS class? Why are we making yo sit here today, having to sffer throgh a corse in operating systems? After all, most of yo will not become OS developers Understand what yo se (and bild!) Understanding how an OS works helps yo develop apps System fnctionality, debgging, performance, secrity, etc. Learn some pervasive abstractions Concrrency: Threads and synchronization are common modern programming abstractions (Java,.NET, etc.) Learn abot complex software systems Many of yo will go on to work on large software projects OS serve as examples of an evoltion of complex systems 18

19 Qestions for today Why do we need operating systems corse? Why do we need operating systems? What does an operating system need to do? Looking back, looking forward 19

20 Why have an OS? What if applications ran directly on hardware? Applications Hardware Problems: Portability Resorce sharing 20

21 What is an OS? The operating system is the software layer between ser applications and the hardware Applications Operating System Hardware The OS is all the code that yo didn t have to write to implement yor application 21

22 Qestions for today Why do we need operating systems corse? Why do we need operating systems? What does an operating system need to do? Looking back, looking forward. 22

23 Roles an OS plays Beatician that hides all the gly low level details so that anyone can se a machine (e.g., smartphone!) Wizard that makes it appear to each program that it owns the machine and shares resorces while making them seem better than they are Referee that arbitrates the available resorces between the rnning programs efficiently, safely, fairly, and secrely Managing a million crazy things happening at the same time is part of that Elephant that remembers all yor data and makes it accessible to yo -- persistence 23

24 More technically Abstraction: defines a set of logical resorces (objects) and well-defined operations on them (interfaces) Virtalization: Isolates and mltiplexes physical resorces via spatial and temporal sharing Access Control: who, when, how Schedling (when): efficiency and fairness Permissions (how): secrity and privacy 24

25 Fndamental OS Isses The fndamental isses/qestions in this corse are: Strctre: how is an operating system organized? Sharing: how are resorces shared among sers? Naming: how are resorces named (by sers and programs)? Protection: how are sers/programs protected from each other? Secrity: how can information access/flow be restricted? Commnication: how to exchange data? Reliability and falt tolerance: how to mask failres? Extensibility: how to add new featres? 26

26 Other Qestions to Ponder What is part of an OS? What is not? Is the windowing system part of an OS? Browser? Java? Apache server? Compiler? Firmware? How different/similar between OS? Windows, Linx, macos, Android, ios, etc. What are the drivers of OS change? Performance, fnctionality, sability, secrity, etc. The UNIX Operating System What are the most compelling isses facing OS today? 27

27 For next class Browse the corse web (especially xv6 docs) Read modle 2 in textbook Start tinkering with xv6 attempting lab 0 finding a partner for project grop 28