cisc 3595/5595 operating systems introductionstorm.cis.fordham.edu/zhang/cs3595_f15/slides/...3 ding...
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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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
What is an OS?Anyone?!!Give a few names of an OS?!! Desktops?!! Smart phones?
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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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
Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
What does an OS do?Resources!! Allocation!! Protection!! Reclamation!! Virtualization
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Ding Yuan, ECE344 Operating System
What does an OS do?Resources!! Allocation!! Protection!! Reclamation!! Virtualization
• Finite resources • Competing demands !• Examples:
• CPU • Memory • Disk • Network
Government: Limited budget,
Land, Natural resources
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Ding Yuan, ECE344 Operating System
What does an OS do?Resources!! Allocation!! Protection!! Reclamation!! Virtualization
• You can’t hurt me, I can’t hurt you. !!• Some degrees of safety and security
Government: Law and order
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Ding Yuan, ECE344 Operating System
What does an OS do?Resources!! Allocation!! Protection!! Reclamation!! Virtualization
• The OS gives, The OS takes away !!• Some times involun- tarily
Government: Income Tax
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Ding Yuan, ECE344 Operating System
What does an OS do?Resources!! Allocation!! Protection!! Reclamation!! Virtualization
• Illusion of infinite, private resources
• Memory vs. disk • Time-shared CPU
Government: Social welfare and
insurance
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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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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Ding Yuan, ECE344 Operating System
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"
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
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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Ding Yuan, ECE344 Operating System
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 !
! 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!
Ding Yuan, ECE344 Operating System
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 !
! 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
Ding Yuan, ECE344 Operating System
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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