CISC 3595/5595 Operating Systems Introductionstorm.cis.fordham.edu/zhang/cs3595_f15/slides/...3 Ding Yuan, ECE344 Operating System Goals of this course 䡦Understand operating system

CISC 3595/5595 Operating SystemsIntroduction

Ding Yuan, ECE344 Operating System

Content of this lectureCourse information (organization, assessment, overview)!Why learning OS?!What is an OS? What does it do?!Computer Hardware: an overview!Summary

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Why learning OS?Fulfill requirement?!Operating System knowledge is important!! http://www.youtube.com/watch?v=-3Rt2_9d7Jg!

! Which course is this?!! http://matt-welsh.blogspot.ca/2010/10/in-defense-of-mark-zuckerberg.html!

! Software companies love OS students!! Most big software companies have system positions

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http://www.youtube.com/watch?v=-3Rt2_9d7Jg

http://matt-welsh.blogspot.ca/2010/10/in-defense-of-mark-zuckerberg.html


Goals of this courseUnderstand operating system concepts!How OS works, and more importantly, why?!! What are the reasons motivated each design?!Basis for future learning!Get hands dirty!! Implement parts of OS!! System programming

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PrerequisiteData Structure, CISC 2200 !And, Computer organizations (CISC 3593) preferred !! What is an Instruction (e.g., load, store)?!! What is CPU? Memory? Registers?!! What is Stack? Stack pointer? !! What is Program Counter (PC)?!We will review the above hardware concepts today…

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Course ContentsOverview of computer hardware !Threads and processes!Synchronization and concurrency!Scheduling!Memory Management, Virtual Memory!Disk Management and File Systems!Advanced topics

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CommunicationsClass web site: http://storm.cis.fordham.edu/zhang/cs3595!! Provides slides, agenda, grading policy, etc.!! All information regarding assignments!

Email me anytime, please include CISC3595 in the subject !Office hour: LC LL812 (lab) for one hour before class!

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ExamMidterm!! Covers first half of class !Final!! Covers second half of class + selected material from first part!Project-related knowledge may be included in the exams

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Cheating policyAcademic integrity!Your work in this class must be your own – we have zero tolerance policy towards cheating of any kind and any student who cheats will get a failing grade in the course!Both the cheater and the student who aided the cheater will be held responsible for the cheating!We have tools to detect software plagiarism

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How NotTo pass?Do not come to lecture!! It’s nice out, the slides are online, and material in the book

anyway!! TRUTH: Lecture material is the basis for exams!! It is much more efficient to learn through discussion!Copy other people’s project!! It is cheating!!! How can you answer the questions in midterm or final

exams?

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How NotTo pass? (2)Do not ask questions in lecture, office hours, or piazza!! It’s scary, I don’t want to embarrass myself!! TRUTH: asking questions is the best way to clarify lecture

material at the time it is being presented!! “There is no such things as stupid question…”!

Wait until the last couple of days to start a project!! The project cannot be done in the last few days!! Repeat: the project cannot be done in the last few days!

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What is an OS?Anyone?!!Give a few names of an OS?!! Desktops?!! Smart phones?

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What is an OS?“Code” that:!! Sits between programs & hardware!! Sits between different programs!! Sits between different users!But what does it do?!! Managing the hardware resource!! Provide a clean set of interface to programs!A good OS is a piece of software that normally you shouldn’t notice of its existence!! But you feel the pain if it goes wrong!Real life analogy?!! Government

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What is an Operating System?

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• A program that acts as an intermediary between a user of a computer and the computer hardware!

• Operating system goals:!– Execute user programs and make solving user

problems easier!– Provide abstractions to application programs: make

computer system convenient to use!– Provide orderly, controlled, efficient allocation of

resources

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OS is…Software layer between hardware and applications !!!!!!!The OS is “all the code that you didn’t have to write” to implement your application

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Four Components of a Computer System

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People, machines, other computers

CPU, memory, I/O devices


An example comparing life Life with an OS!file = open (“test.txt”, O_WRONLY);!

write (file, “test”, 4);!

close (file);

Life without an OS

• Blocks, platter, track, and sector

• Where is this file on disk? Which platter, track, and sectors?

• Code needs to change on a different system

!

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OS and hardwareThe OS abstracts/controls/mediates access to hardware resources (what resources?) ! Computation (CPUs)!! Volatile storage (memory) and persistent storage (disk, etc.)!! Communication (network, modem, etc.)!! Input/output devices (keyboard, display, printer, etc.)

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Benefits to ApplicationsSimpler!! no tweaking device registers!Device independent!! all disks look the same!Portable!! same program runs on Windows95/98/ME/NT/2000/XP/Vista/

Windows 7/Windows 8!Worry less about interference from other applications

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What does an OS do?Resources!! Allocation!! Protection!! Reclamation!! Virtualization

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• Finite resources • Competing demands !• Examples:

• CPU • Memory • Disk • Network

Government: Limited budget,

Land, Natural resources

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• You can’t hurt me, I can’t hurt you. !!• Some degrees of safety and security

Government: Law and order

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• The OS gives, The OS takes away !!• Some times involun- tarily

Government: Income Tax

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• Illusion of infinite, private resources

• Memory vs. disk • Time-shared CPU

Government: Social welfare and

insurance

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Why you want to learn OS?Foundation to other software!! Databases, Browsers, Computational software, … …!OS is one of the hardest software piece to write & debug!! Directly talks to hardware (very ugly interfaces)!! Abstract into clean interfaces!! They are BIG!! Lines of code:!

! Windows Vista (2006): 50M (XP + 10M)!! Linux 3.6: 15.9 M!! Android 4.0: > 1M

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Why you want to learn OS?Many OS concepts (e.g., protection, resource management) is needed in other places!! E.g., browser!OS is used everywhere!! Your car is running on Linux/Windows

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Content of this lectureCourse information (organization, assessment, overview)!Why learning OS?!What is an OS? What does it do?!History of OS!Computer Hardware: an overview!! Basic Elements!! Processor: Instruction Execution!! Memory Hierarchy!

! Cache Memory!! I/O Communication Techniques !

! Summary27

History of Operating Systems! First generation (1945–55): vacuum tubes, bugs, no

operating systems, programming in machine code or plugboard !

! Second generation (1955–65): transistors, batch systems, programming in assembly, FORTRAN!

! Third generation (1965–1980): ICs, multiprogramming OS (to increase utilization of CPU), timesharing!

! Fourth generation (1980–present) personal computers, (CP/M, DOS, Windows), GUI!

! The fifth generation (1990–present) mobile computers

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Glen Beck and Betty Snyder program ENIAC. (U.S. Army photo)

ENIAC (Electronic Numerical Integrator And Computer) ! was the first electronic general-purpose computer. It wasTuring-complete, digital, and can be reprogrammed to solve "a large class of !numerical problems"

http://en.wikipedia.org/wiki/Betty_Holberton

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Turing_complete

307IBM/360 (2 million, 5 billion to built (budget 2 million)),! jewel of the office, Batch system

318 1970s, Unix System, PDF-7 (mini-computer)

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DOS for Apple II: Contract

https://s3.amazonaws.com/s3data.computerhistory.org/atchm/documents/102723982-05-01-acc.pdf

Current Generation OS ! Mobile devices (Smartphone, wearable

computers…) !! Limited power!! Different I/O: touch screen, cecullar communicaiton,

sensors, …!! Android, iOS, Windows !

! Android's kernel is based on one of the Linux kernel's long-term support (LTS) branches!

! iOS (based upon Mac OS) !! iPhone, iPod, iPad, … !

! …

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! Summary34

Computer System Organization

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! One or more CPUs, device controllers connected through common bus providing access to shared memory

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Basic Hardware Elements! Processor or Central Processing Unit (CPU)!

! Controls operation, performs data processing!! Memory (main/primary memory)!

! Volatile, i.e., data is typically lost when power is removed!! Used to store data and instructions!

! I/O Modules: disk controller, USB controller, ...!! Moves data between computer and external device such

as storage (e.g. hard drive), communication equipment, terminals!!

! System Bus!! Wires or backplane connecting CPUs, I/O modules and

main memory3613

Processor (CPU)! CPU: the physical heart of entire computer system!

! Execute instructions!! Instruction set: the set of machine instructions that a

processor can execute, main categories: !! Processor-memory: move data between memory and

processor!! processor-I/O: move data between peripheral device and

CPU!! Data processing: arithmetic or logic operation on data!! Control: alter execution sequence (jump, if and loop

structure)!! Some instructions are privilege instructions (can only

be executed by os kernel).3714

Stored Program Computer! A program: a sequence of instructions stored in

memory (main memory or disk)!! when running a program, it is loaded (from disk) into main

memory !! Basic Instruction Execution cycle:!

! Processor reads (fetches) instruction from main memory!! Processor executes the instruction

38Stored program computer (due to John von Neumann (1903-1957))

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Top-Level Logic View

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Main memory:!a large array of words or bytes. Each words has its own address.

CPU registers: in-CPU memory,!faster and smaller than main memory!

CPU Registers: data and address registers! Data/Address registers: store data or memory

address !! Store frequently used variable in register: !! for (register int i = 0; i < bufsize; i++) * p++ =

assigned_val; !! Usually compiler decides what variables to store in

register

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CPU: Control and Status Registers! Control CPU operation, and stores CPU status !

! Program counter (PC): holds address of the instruction to be fetched next!

! Instruction register (IR): store the instruction to be executed!

! Program status word (PSW): contain bits set by processor hardware as a result of operations!! Condition code bits (set by comparison instructions)!! CPU priority!! Mode (user, or kernel mode): OS kernel runs in kernel supervisor

mode, other programs run in user mode!! Other …

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Machine code and Assembly Language! CPU only understands binary => machine

instructions are coded in binary strings!! e.g., 10110000 01100001 (Hexadecimal: B0 61)!

! Assembly language: mnemonic language (helping to remember)!! MOV AL, #61h!! Move the value 61h (or 97 decimal; the h-suffix means

hexadecimal; the pound sign means move the immediate value, not location) into the processor register named "AL".

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Considering a Hypothetical Machine

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Singleprocessor & Multiprocessor

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! Most systems use a single general-purpose processor!

! Multiprocessors systems growing in use and importance!! parallel systems, tightly-coupled systems!! Advantages include!1. Increased throughput!2. Economy of scale!3. Increased reliability – graceful degradation or fault

tolerance

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Outline

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• What is operating system? !• Necessary background: computer hardware

organization!! Basic Elements!! Processor: Instruction Execution!! Memory Hierarchy!

! Cache Memory!! I/O Communication Techniques

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Memory Hierarchy

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! CPU register!! CPU L1 cache!! Main memory, RAM – volatile storage media that

CPU can access directly!! Random access: take same amount of time to access

any part of the memory!! Hard disk: Large nonvolatile storage capacity!

! disk controller: determines logical interaction between the device and the computer !

! Magnetic tape: !! sequential access: recall that you have to rewind

VCR?47

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Performance measure: maximum transfer rate; spindle Rotation Speed: decides the reading/writing rate; seek time: avg time to locate the data

Why so many different memory/storage! Major constraints in memory!

! Amount, Speed, Expense!! Generally:!

! Faster access time, greater cost per bit

4926 ns: nanosecond (10-9 seconds), 1 billionth second

Memory Hierarchy! Goal: to obtain good trade-off between cost and

performance!! Going down hierarchy!

! Decreasing cost per bit!! Increasing capacity!! Increasing access time!! Decreasing frequency of access

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Memory Hierarchy and Caching

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! Caching: information in use is copied from slower and larger storage to faster and smaller storage (cache) temporarily!! Faster storage (cache) checked first to determine if information

is there!! If it is, information used directly from the cache (fast)!! If not, data copied to cache and used there!

! Exploit temporal locality and spatial locality!! Data which is required soon is often close in memory to the current

data!! Caching is performed at many levels in a computer!

! Hardware: L1 cache!! Operating system: disk cache in memory!! Software/application level caching

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Primary Cache (L1 cache)! Processor must access memory at least once per

instruction cycle!! Processor speed faster than memory access speed!

! Solution: L1 Cache, storage on CPU for temporary storage of instructions and data

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• Cache contains copy of a portion of main memory!• CPU first checks cache!

•If not found, block of memory read into cache!• Because of locality of reference, likely future memory references are in that block!




! Summary53

Input/Output Device Controller

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• Device Controller:!• A chip or sets of chip that control I/O device to perform I/O!• Special purpose processor: execute concurrently with

CPU!• Basic functionalities: moving data between device and

controller’s local buffer!• Has local buffer (registers): CPU communicates with

device controller through these, e.g., command, status, input/output data!

• Device driver: software that talks to device controller

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I/O operation modes! Coordination between CPU and Device Controller!! Programmed I/O: I will wait here until you are done with

this, “busy waiting”!! Problem: most I/O devices are slower than CPU => inefficient for

CPU to wait for I/O to complete!!

! Interrupt-driven I/O: let me know as soon as you are done... !

! Direct memory access (DMA): Work on the reports and when you are done, put them in my mail box, and let me know... !!

! Needs a mechanism to change the sequential instruction execution of CPU5533

Interrupts! A mechanism to interrupt normal execution sequence

of CPU! !! Recall CPU follows the fetch/execution cycle

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Interrupt Handler:!Predefined routines !to be called when!a certain interrupt !occurs.

Different Types of Interrupts ! Program generated: arithmetic overflow, division by

zero, illegal machine instruction, reference outside of user’s allowed memory space, also called exception, trap or software interrupt!

! Timer: generated by a timer with CPU !! I/O: generated by I/O controller to signal completion

of operation or error condition!! Delivered to CPU via bus, together with device number!

! Hardware failure: triggered by power failure, memory parity error…

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An operating system is interrupt driven.

Interrupt-driven I/O

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! When CPU encounters an I/O related instruction!! it executes that instruction by issuing a command to

appropriate I/O module, and ask I/O module to give an interrupt when done!

! CPU continues to do its work without waiting for I/O completion (maybe running other programs if it’s a blocking call, such as cin, scanf…)… !

! After I/O device controller finish I/O operation, it generate an interrupt to inform CPU!

! CPU, in interrupt handler, read data from device controller or write next block of data to device controller, and wake up processes waiting for the interrupt...

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Direct Memory Access (DMA) I/O

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! DMA: allow device to access memory for reading and/or writing independently of CPU. !! Used in high-speed I/O devices: disk controllers, graphics

cards, network cards and sound cards!! DMA module (DMA device controller)!

! Transfers blocks of data from buffer storage directly to main memory!

! Only one interrupt is generated per block!! CPU only involved at beginning and ending transfer.!

! Less CPU intervention => much more efficient in terms of processing times

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Multiprogramming

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! Multiple programs are kept in memory, i.e., process (a program in execution)!! One process is selected and run via CPU

scheduling!! When it has to wait (e.g., for I/O), OS

switches to another process!! After saving status of pending process

(PC, stack, …) !! After an interrupt handler completes,

control may not return to the program that was executing at the time of the interrupt!

! Timesharing: allocate CPU to different processes in small quota, and round-robin manner60


Before the next classBrowse the course web!Start thinking about partners for project groups!Read chapter 1 !See me up front if you have any questions!Let the fun (or grind) begin!

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Documents

CISC 3595/5595 Operating Systems Introductionstorm.cis.fordham.edu/zhang/cs3595_f15/slides/...3 Ding Yuan, ECE344 Operating System Goals of this course 䡦Understand operating system