程序代写代做代考 kernel compiler game cache database Chapter 1: Introduction

Chapter 1: Introduction
EECS 3221

What is an Operating System?
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 Make the computer system convenient to use
Use the computer hardware in an efficient manner
Operating System Concepts – 9th Edition 1.2 Silberschatz, Galvin and Gagne ©2013

Computer System Structure
Computer system can be divided into four components: Hardware – provides basic computing resources
 CPU, memory, I/O devices Operating system
 Controls and coordinates use of hardware among various applications and users
Application programs – define the ways in which the system resources are used to solve the computing problems of the users
 Word processors, compilers, web browsers, database systems, video games
Users
 People, machines, other computers
Operating System Concepts – 9th Edition 1.3 Silberschatz, Galvin and Gagne ©2013

Four Components of a Computer System
Operating System Concepts – 9th Edition 1.4 Silberschatz, Galvin and Gagne ©2013

What Operating Systems Do
Depends on the point of view
Users want convenience, ease of use
Don’t care about resource utilization
But shared computer such as mainframe or minicomputer must keep all
users happy
Users of dedicate systems such as workstations have dedicated resources
but frequently use shared resources from servers
Handheld computers are resource poor, optimized for usability and battery
life
Some computers have little or no user interface, such as embedded computers in devices and automobiles
Operating System Concepts – 9th Edition 1.5 Silberschatz, Galvin and Gagne ©2013

Operating System Definition
OS is a resource allocator Manages all resources
Decides between conflicting requests for efficient and fair resource use
OS is a control program
Controls execution of programs to prevent errors and improper use
of the computer
Operating System Concepts – 9th Edition 1.6 Silberschatz, Galvin and Gagne ©2013

Operating System Definition (Cont.)
No universally accepted definition
“Everything a vendor ships when you order an operating system” is good approximation
But varies wildly
“The one program running at all times on the computer” is the kernel. Everything else is either a system program (ships with the operating system) or an application program.
Operating System Concepts – 9th Edition 1.7 Silberschatz, Galvin and Gagne ©2013

Computer System Organization
Computer-system organization
One or more CPUs, device controllers connect through common bus providing access to shared memory
Concurrent execution of CPUs and devices competing for memory cycles
Operating System Concepts – 9th Edition 1.8 Silberschatz, Galvin and Gagne ©2013

Computer-System Operation
I/O devices and the CPU can execute concurrently
Each device controller is in charge of a particular device type
Each device controller has a local buffer
The device driver for each device moves data from/to main memory to/from local buffers
The device controller is responsible for moving the data between the peripheral devices that it controls and its local buffer storage.
Device controller informs CPU that it has finished its operation by causing an interrupt
Operating System Concepts – 9th Edition 1.9 Silberschatz, Galvin and Gagne ©2013

Common Functions of Interrupts
Hardware may trigger an interrupt at any time by sending a signal to the CPU, usually by way of the system bus.
A trap or exception is a software-generated interrupt caused either by an error or a user request
Software error or request creates exception or trap Division by zero, request for operating system service
Other process problems include infinite loop, processes modifying each other or the operating system
An operating system is interrupt driven
Operating System Concepts – 9th Edition 1.10 Silberschatz, Galvin and Gagne ©2013

Interrupt Handling
The operating system preserves the state of the CPU by storing registers and the program counter
Separate segments of code determine what action should be taken for each type of interrupt
Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines
Interrupt architecture must save the address of the interrupted instruction
Operating System Concepts – 9th Edition 1.11 Silberschatz, Galvin and Gagne ©2013

Interrupt Related Concepts
Interrupt number: identifies the type of interrupt – provided by the interrupt h/w architecture whenever an interrupt occurs – is used as an index into the interrupt vector to lookup the address of the service routine for each interrupt.
Program counter: contains address of instruction to be executed next by the CPU – a h/w CPU register – the interrupt h/w architecture automatically first saves PC value whenever an interrupt occurs.
Process: a program in execution.
Process Control Block (PCB): stores important system information about
each process.
System call: special instruction to invoke the OS, by generating an interrupt, to perform an OS-related service – a number i is associated with each type of system call, and is used as an index into a system call table to look up the address of the program which implements each type of system call.
CPU Scheduler: selects a process from the processes in memory that are ready to execute and allocates the CPU to that process. (OS-ch-3.9-3.10)
Operating System Concepts – 9th Edition 1.12 Silberschatz, Galvin and Gagne ©2013

Interrupt Timeline
Operating System Concepts – 9th Edition 1.13 Silberschatz, Galvin and Gagne ©2013

Interrupt-Driven I/O Cycle
Operating System Concepts – 9th Edition 1.14 Silberschatz, Galvin and Gagne ©2013

Interrupt-Vector Table
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Multiprogramming System
Operating System Concepts – 9th Edition 1.16 Silberschatz, Galvin and Gagne ©2013

Process State
Operating System Concepts – 9th Edition 1.17 Silberschatz, Galvin and Gagne ©2013

Process Control Block (PCB)
Operating System Concepts – 9th Edition 1.18 Silberschatz, Galvin and Gagne ©2013

Computer Startup
bootstrap program is loaded at power-up or reboot
Typically stored in ROM or EPROM, generally known as firmware Initializes all aspects of system
Loads operating system kernel and starts execution
Operating System Concepts – 9th Edition 1.22 Silberschatz, Galvin and Gagne ©2013

Dual Mode Operation
Dual-mode operation allows OS to protect itself and other system components User mode and kernel mode
Mode bit provided by hardware
 Provides ability to distinguish when system is running user code or kernel code
 Some instructions designated as privileged, only executable in kernel mode
 System call changes mode to kernel, return from call resets it to user Increasingly CPUs support multi-mode operations
i.e. virtual machine manager (VMM) mode for guest VMs
Operating System Concepts – 9th Edition 1.23 Silberschatz, Galvin and Gagne ©2013

Timer to Prevent Infinite Loop or Process Hogging Resources
Timer to prevent infinite loop / process hogging resources Set interrupt after specific period
Operating system decrements counter
When counter zero generate an interrupt
Set up before scheduling process to regain control or terminate program that exceeds allotted time
Operating System Concepts – 9th Edition 1.26 Silberschatz, Galvin and Gagne ©2013

Interrupt Handling Diagram
User Mode (mode bit = 0)
Register
R1
R1 =
…
91
? (1) read()
91 is a system call … which, when
executed, generates
a software interrupt (trap), system enters kernel mode
Kernel Mode (mode bit =1)
Program Counter
PC = Y
…
…
Interrupt
P1’s PCB
Service Routine (ISR)
…
PC=3224
R1=91
…
h/w location for storing PC return
addres
s
3224
PC
Program Counter
PC = … 3222 3223 3224 …
(9) P1 resumes execution at address 3224 where it was interrupted
(4) Interrupt Service Routine at address Y is executed
PC
User Process P1
…
(5) save P1’s context into P1’s PCB
…
enter P1’s PCB into I/O wait queue
…
handle interrupt …
return
(6) The
system call number i
of read( ) is used as 0 index into 1 System call … table
…… …
System call table
Interrupt Vector
(2) h/w saves PC return address 3224
(3) The
0
1 …
X …
Progra m Counter
PC
Read( ) system call routine
U
…
R1 <- 2; read( ); ... ... PC = iU Y ... call I/O driver ... return interrupt number X of interrupt type system call is used as index into Interrupt Vector (8) If P1 selected Dispatche r restore P1’s context from P1’s PCB Copyright © 2020 Jia Xu. All rights reserved. (7) Read system call routine at address U executed CPU scheduler Direct Memory Access Structure Used for high-speed I/O devices able to transmit information at close to memory speeds Device controller transfers blocks of data from buffer storage directly to main memory without CPU intervention Only one interrupt is generated per block, rather than the one interrupt per byte Operating System Concepts – 9th Edition 1.28 Silberschatz, Galvin and Gagne ©2013 Storage Definitions and Notation Review Operating System Concepts – 9th Edition 1.29 Silberschatz, Galvin and Gagne ©2013 Storage Structure Main memory – only large storage media that the CPU can access directly Random access Typically volatile Secondary storage – extension of main memory that provides large nonvolatile storage capacity Magnetic disks – rigid metal or glass platters covered with magnetic recording material Disk surface is logically divided into tracks, which are subdivided into sectors The disk controller determines the logical interaction between the device and the computer Solid-state disks – faster than magnetic disks, nonvolatile Various technologies Becoming more popular Operating System Concepts – 9th Edition 1.30 Silberschatz, Galvin and Gagne ©2013 Storage Hierarchy Storage systems organized in hierarchy Speed Cost Volatility Caching – copying information into faster storage system; main memory can be viewed as a cache for secondary storage Device Driver for each device controller to manage I/O Provides uniform interface between controller and kernel Operating System Concepts – 9th Edition 1.31 Silberschatz, Galvin and Gagne ©2013 Storage-Device Hierarchy Operating System Concepts – 9th Edition 1.32 Silberschatz, Galvin and Gagne ©2013 Performance of Various Levels of Storage Movement between levels of storage hierarchy can be explicit or implicit Operating System Concepts – 9th Edition 1.33 Silberschatz, Galvin and Gagne ©2013 How A Modern Computer System Works Operating System Concepts – 9th Edition 1.34 Silberschatz, Galvin and Gagne ©2013 Computer-System Architecture Most systems use a single general-purpose processor (PDAs through mainframes) Most systems have special-purpose processors as well Multiprocessors systems growing in use and importance Also known as parallel systems, tightly-coupled systems Advantages include: 1. Increased throughput 2. Economy of scale 3. Increased reliability – graceful degradation or fault tolerance Two types: 1. Asymmetric Multiprocessing 2. Symmetric Multiprocessing Operating System Concepts – 9th Edition 1.35 Silberschatz, Galvin and Gagne ©2013 Symmetric Multiprocessing Architecture Operating System Concepts – 9th Edition 1.36 Silberschatz, Galvin and Gagne ©2013 A Dual-Core Design Operating System Concepts – 9th Edition 1.37 Silberschatz, Galvin and Gagne ©2013 Computer System Components Operating System Concepts – 9th Edition 1.38 Silberschatz, Galvin and Gagne ©2013 Non-Uniform Memory Access Operating System Concepts – 9th Edition 1.39 Silberschatz, Galvin and Gagne ©2013 PC Motherboard Operating System Concepts – 9th Edition 1.40 Silberschatz, Galvin and Gagne ©2013 Clustered Systems Like multiprocessor systems, but multiple systems working together Usually sharing storage via a storage-area network (SAN) Provides a high-availability service which survives failures  Asymmetric clustering has one machine in hot-standby mode  Symmetric clustering has multiple nodes running applications, monitoring each other Some clusters are for high-performance computing (HPC)  Applications must be written to use parallelization Operating System Concepts – 9th Edition 1.41 Silberschatz, Galvin and Gagne ©2013 Clustered Systems Operating System Concepts – 9th Edition 1.42 Silberschatz, Galvin and Gagne ©2013 Computing Environments Many different kinds of computing environments Traditional computing Mobile computing Client Server computing Peer-to-Peer computing Cloud computing Virtualization Real-Time Embedded Systems Open Source Operating Systems Operating System Concepts – 9th Edition 1.43 Silberschatz, Galvin and Gagne ©2013 Client Server Computing Operating System Concepts – 9th Edition 1.44 Silberschatz, Galvin and Gagne ©2013 Peer-to-Peer Computing Operating System Concepts – 9th Edition 1.45 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Cloud Computing Delivers computing, storage, even apps as a service across a network Logical extension of virtualization as based on virtualization Amazon EC2 has thousands of servers, millions of VMs, PBs of storage available across the Internet, pay based on usage Many types Public cloud – available via Internet to anyone willing to pay Private cloud – run by a company for the company’s own use Hybrid cloud – includes both public and private cloud components Software as a Service (SaaS) – one or more applications available via the Internet (i.e. word processor) Platform as a Service (PaaS) – software stack ready for application use via the Internet Ex: LAMP (Linux (OS), Apache (web server), MySQL (DB), PHP, Perl or Python (programming languages) Infrastructure as a Service (IaaS) – servers or storage available over Internet (i.e. storage available for backup use) Operating System Concepts – 9th Edition 1.46 Silberschatz, Galvin and Gagne ©2013 Cloud Computing Operating System Concepts – 9th Edition 1.47 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Virtualization Allows operating systems to run applications within other OSes Vast and growing industry Virtualization – OS natively compiled for CPU, running guest OSes also natively compiled Consider VMware running WinXP guests, each running applications, all on native WinXP host OS VMM provides virtualization services Operating System Concepts – 9th Edition 1.48 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Virtualization Use cases involve laptops and desktops running multiple OSes for exploration or compatibility Apple laptop running Mac OS X host, Windows as a guest Developing apps for multiple OSes without having multiple systems QA testing applications without having multiple systems Executing and managing compute environments within data centers Operating System Concepts – 9th Edition 1.49 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Virtualization Operating System Concepts – 9th Edition 1.50 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Real-Time Embedded Systems Real-time embedded systems most prevalent form of computers Vary considerable, special purpose, limited purpose OS, real-time OS Use expanding Many other special computing environments as well Some have OSes, some perform tasks without an OS Real-time OS has well-defined fixed time constraints Processing must be done within constraint Correct operation only if constraints met Operating System Concepts – 9th Edition 1.51 Silberschatz, Galvin and Gagne ©2013 Open-Source Operating Systems Operating systems made available in source-code format rather than just binary closed-source Counter to the copy protection and Digital Rights Management (DRM) movement Started by Free Software Foundation (FSF), which has “copyleft” GNU Public License (GPL) Examples include GNU/Linux and BSD UNIX (including core of Mac OS X), and many more Operating System Concepts – 9th Edition 1.52 Silberschatz, Galvin and Gagne ©2013 End of Chapter 1 EECS 3221

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