Lecture Operating system concepts (9/ed) - Chapter 2: Operating-System

Chapter 2: Operating-System Structures

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Operating System Concepts – 9th Edition

Chapter 2: Operating-System Structures

(cid:0) Operating System Services

(cid:0) User Operating System Interface

(cid:0) System Calls

(cid:0) Types of System Calls

(cid:0) System Programs

(cid:0) Operating System Design and Implementation (cid:0) Operating System Structure (cid:0) Operating System Debugging (cid:0) Operating System Generation

(cid:0) System Boot

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2.2 Operating System Concepts – 9th Edition

Objectives

(cid:0)

To describe the services an operating system provides to users, processes, and other systems

(cid:0)

To discuss the various ways of structuring an operating system

(cid:0)

To explain how operating systems are installed and customized and how they boot

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2.3 Operating System Concepts – 9th Edition

Operating System Services

Operating systems provide an environment for execution of programs and services to programs and users

(cid:0)

One set of operating-system services provides functions that are helpful to the user: (cid:0) User interface - Almost all operating systems have a user

interface (UI).

 Varies between Command-Line (CLI), Graphics User

(cid:0)

Interface (GUI), Batch

(cid:0)

Program execution - The system must be able to load a program into memory and to run that program, end execution, either normally or abnormally (indicating(cho biết) error)

(cid:0)

I/O operations - A running program may require I/O, which may involve(gồm) a file or an I/O device

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2.4 Operating System Concepts – 9th Edition

Operating System Services (Cont.)

One set of operating-system services provides functions that are helpful to the user (Cont.):

(cid:0)

File-system manipulation - The file system is of particular(đ/biệt) interest. Programs need to read and write files and directories, create and delete them, search them, list file Information, permission management.

(cid:0) Communications – Processes may exchange(trao đổi DL) information,

on the same computer or between computers over a network

 Communications may be via shared memory or through message

passing (packets(gói tin) moved by the OS)

(cid:0)

Error detection – OS needs to be constantly(l/luôn) aware(có kiến thức, nhận thức) of possible errors

 May occur in the CPU and memory hardware, in I/O devices, in user

program

 For each type of error, OS should take the appropriate action to ensure(đảm bảo) correct and consistent(nhất quán) computing

 Debugging facilities(p/tiện) can greatly enhance(n/cao) the user’s and programmer’s abilities(k/năng) to efficiently(h/quả) use the system

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2.5 Operating System Concepts – 9th Edition

Operating System Services (Cont.)

Another set of OS functions exists for ensuring the efficient operation of the system itself via resource sharing (cid:0) Resource allocation - When multiple users or multiple jobs running

concurrently, resources must be allocated to each of them

 Many types of resources - CPU cycles, main memory, file storage,

I/O devices.

(cid:0) Accounting(tính toán, giải thích) - To keep track of which users use

how much and what kinds of computer resources

(cid:0)

Protection and security - The owners of information stored in a multiuser or networked computer system may want to control use of that information, concurrent processes should not interfere with each other

 Protection involves(gồm) ensuring(đ/bảo) that all access to system

resources is controlled

 Security of the system from outsiders requires user

authentication(xác thực), extends to defending(b/vệ) external I/O devices from invalid(ko hợp lệ) access attempts(nỗ lực)

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2.6 Operating System Concepts – 9th Edition

A View of Operating System Services

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2.7 Operating System Concepts – 9th Edition

User Operating System Interface - CLI

CLI or command interpreter(th/dịch) allows direct command

entry(mục nhập) (cid:0) Sometimes implemented in kernel, sometimes by systems

program

(cid:0) Sometimes multiple flavors implemented – shells (cid:0) Primarily(chủ yếu) fetches(tìm nạp) a command from user

and executes it

(cid:0) Sometimes commands built-in, sometimes just names of

programs  If the latter, adding new features doesn’t require shell

modification

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2.8 Operating System Concepts – 9th Edition

Bourne Shell Command Interpreter

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2.9 Operating System Concepts – 9th Edition

User Operating System Interface - GUI

(cid:0)

User-friendly desktop metaphor(ẩn dụ) interface (cid:0) Usually mouse, keyboard, and monitor

(cid:0) Icons represent files, programs, actions, etc

(cid:0) Various mouse buttons over objects in the interface cause

various actions (provide information, options, execute function, open directory (known as a folder)

(cid:0) Invented at Xerox(sao chụp) PARC

(cid:0) Many systems now include both CLI and GUI interfaces (cid:0) Microsoft Windows is GUI with CLI “command” shell (cid:0) Apple Mac OS X is “Aqua” GUI interface with UNIX kernel

underneath(ở dưới) and shells available

(cid:0) Unix and Linux have CLI with optional(tuỳ ý) GUI interfaces

(CDE, KDE, GNOME)

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2.10 Operating System Concepts – 9th Edition

Touchscreen Interfaces

(cid:0)

desired(m/muốn)

Touchscreen devices require new interfaces (cid:0) Mouse not possible or not

Actions and selection based on gestures

(cid:0)

Virtual keyboard for text entry

(cid:0)

Voice commands.

(cid:0)

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2.11 Operating System Concepts – 9th Edition

The Mac OS X GUI

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2.12 Operating System Concepts – 9th Edition

System Calls

(cid:0) Programming interface to the services provided by the OS

(cid:0)

Typically(điển hình) written in a high-level language (C or C++)

(cid:0) Mostly accessed by programs via a high-level Application Programming Interface (API) rather(đúng hơn) than direct system call use

(cid:0)

Three most common APIs are Win32 API for Windows, POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X), and Java API for the Java virtual machine (JVM)

Note that the systemcall names used throughout this text are generic(chung)

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2.13 Operating System Concepts – 9th Edition

Example of System Calls

(cid:0) System call sequence to copy the contents of one file to another file

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2.14 Operating System Concepts – 9th Edition

Example of Standard API

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2.15 Operating System Concepts – 9th Edition

System Call Implementation

(cid:0)

Typically(điển hình), a number associated(l/kết tệp với 1 ứng dụng)) with each system call (cid:0) System-call interface maintains(giữ) a table indexed

according(theo) to these numbers

(cid:0)

The system call interface invokes(gọi) the intended(mong đợi) system call in OS kernel and returns status of the system call and any return values

(cid:0)

The caller need know nothing about how the system call is implemented

(cid:0)

Just needs to obey(tuân theo) API and understand what OS will do as a result call

(cid:0) Most details of OS interface hidden from programmer by API  Managed by run-time support library (set of functions built

into libraries included with compiler)

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2.16 Operating System Concepts – 9th Edition

API – System Call – OS Relationship

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2.17 Operating System Concepts – 9th Edition

System Call Parameter Passing

(cid:0) Often, more information is required than simply identity(đồng nhất)

of desired(m/muốn) system call (cid:0) Exact type and amount of information vary(biến đổi) according

to OS and call

(cid:0)

Three general(chung) methods used to pass(chuyển qua) parameters to the OS (cid:0) Simplest: pass the parameters in registers

 In some cases, may be more parameters than registers (cid:0) Parameters stored in a block, or table, in memory, and address

of block passed as a parameter in a register  This approach taken(p/pháp) by Linux and Solaris

(cid:0) Parameters placed, or pushed, onto the stack by the program

and popped off the stack by the operating system

(cid:0) Block and stack methods do not limit the number or length of

parameters being passed

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2.18 Operating System Concepts – 9th Edition

Parameter Passing via Table

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2.19 Operating System Concepts – 9th Edition

Types of System Calls

(cid:0) Process control

(cid:0) create process, terminate process

(cid:0) end, abort(huỷ bỏ ch/trình đang chạy)

(cid:0) load, execute

(cid:0) get process attributes, set process attributes

(cid:0) wait for time (cid:0) wait event, signal event

(cid:0)

(cid:0) allocate and free memory (cid:0) Dump(câm) memory if error (cid:0) Debugger (trình gỡ rối) for determining bugs, single step execution Locks for managing access to shared data between processes

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2.20 Operating System Concepts – 9th Edition

Types of System Calls

(cid:0) File management

(cid:0) create file, delete file

(cid:0) open, close file

(cid:0) read, write, reposition

(cid:0) get and set file attributes

(cid:0) Device management

(cid:0) request device, release device

(cid:0) read, write, reposition

(cid:0) get device attributes, set device attributes

(cid:0) Logically(hợp lý) attach(gắn, đính kèm) or detach devices

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2.21 Operating System Concepts – 9th Edition

Types of System Calls (Cont.)

(cid:0) Information maintenance

(cid:0) get time or date, set time or date

(cid:0) get system data, set system data

(cid:0) get and set process, file, or device attributes

(cid:0) Communications

(cid:0) create, delete communication connection

(cid:0)

send, receive messages if message passing model to host name or process name  From client to server

(cid:0) Shared-memory model create and gain access to memory

regions

(cid:0) transfer status information

(cid:0) attach and detach remote devices

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2.22 Operating System Concepts – 9th Edition

Types of System Calls (Cont.)

(cid:0)

Protection (cid:0) Control access to resources (cid:0) Get and set permissions (cid:0) Allow and deny user access

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2.23 Operating System Concepts – 9th Edition

Examples of Windows and Unix System Calls

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2.24 Operating System Concepts – 9th Edition

Standard C Library Example

(cid:0) C program invoking printf() library call, which calls write() system call

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2.25 Operating System Concepts – 9th Edition

Example: MS-DOS

(cid:0) Single-tasking

(cid:0)

Shell invoked when system booted

(cid:0)

(cid:0) Simple method to run program (cid:0) No process created Single memory space

(cid:0)

Loads program into memory, overwriting all but the kernel

(cid:0)

Program exit -> shell reloaded

At system startup running a program

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2.26 Operating System Concepts – 9th Edition

Example: FreeBSD

(cid:0)

Unix variant (cid:0) Multitasking

(cid:0) User login -> invoke user’s choice of shell

(cid:0)

Shell executes fork() system call to create process (cid:0) Executes exec() to load program into

process

(cid:0) Shell waits for process to terminate or

continues with user commands

(cid:0) Process exits with:

(cid:0) code = 0 – no error

(cid:0) code > 0 – error code

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2.27 Operating System Concepts – 9th Edition

System Programs

(cid:0)

System programs provide a convenient environment for program development and execution. They can be divided into:

(cid:0) File manipulation

(cid:0) Status information sometimes stored in a File modification (cid:0) Programming language support (cid:0) Program loading and execution (cid:0) Communications (cid:0) Background services (cid:0) Application programs

(cid:0) Most users’ view of the operation system is defined by system

programs, not the actual system calls

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2.28 Operating System Concepts – 9th Edition

System Programs

(cid:0)

Provide a convenient environment for program development and execution (cid:0) Some of them are simply user interfaces to system calls; others

are considerably more complex

(cid:0)

File management - Create, delete, copy, rename, print, dump, list, and generally manipulate files and directories

(cid:0)

Status information (cid:0) Some ask the system for info - date, time, amount of available

memory, disk space, number of users

(cid:0) Others provide detailed performance(hiệu năng), logging, and

debugging information

(cid:0)

Typically(điển hình), these programs format and print the output to the terminal or other output devices

(cid:0) Some systems implement a registry(đ/ký) - used to store and

retrieve configuration(thiết lập cấu hình) information

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2.29 Operating System Concepts – 9th Edition

System Programs (Cont.)

(cid:0) File modification

(cid:0) Text editors to create and modify files

(cid:0) Special commands to search contents of files or

perform(thực hiện) transformations(b/đổi) of the text

(cid:0)

Programming-language support - Compilers, assemblers(ch/trình dịch hợp ngữ asembly), debuggers and interpreters sometimes provided

(cid:0)

Program loading and execution- Absolute(chắc chắn) loaders, relocatable loaders, linkage(l/kết) editors, and overlay-loaders, debugging systems for higher-level and machine language

(cid:0)

Communications - Provide the mechanism(cơ cấu) for creating virtual connections among processes, users, and computer systems (cid:0) Allow users to send messages to one another’s screens, browse web pages, send electronic-mail messages, log in remotely, transfer files from one machine to another

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2.30 Operating System Concepts – 9th Edition

System Programs (Cont.)

(cid:0) Background Services

(cid:0)

Launch(khởi chạy) at boot time  Some for system startup, then terminate  Some from system boot to shutdown

(cid:0) Provide facilities(k/năng làm việc thuận lợi, tiện nghi) like disk

checking, process scheduling, error logging, printing

(cid:0) Run in user context(văn cảnh) not kernel context (cid:0) Known as services, subsystems, daemons

(cid:0)

Application programs (cid:0) Don’t pertain(thuộc về) to system (cid:0) Run by users (cid:0) Not typically(thường) considered(xét) part of OS

(cid:0) Launched by command line, mouse click, finger poke

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2.31 Operating System Concepts – 9th Edition

Operating System Design and Implementation

(cid:0)

Design and Implementation of OS not “solvable(có thể g/quyết)”, but some approaches(p/pháp) have proven(đã CM) successful

(cid:0)

Internal structure of different Operating Systems can vary(b/đổi) widely

(cid:0) Start the design by defining goals and specifications

(cid:0) Affected(ả/hưởng) by choice of hardware, type of system

(cid:0)

User goals and System goals (cid:0) User goals – operating system should be convenient to use,

easy to learn, reliable(chắc chắn), safe, and fast

(cid:0) System goals – operating system should be easy to design,

implement, and maintain, as well as flexible(linh hoạt), reliable, error-free, and efficient

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2.32 Operating System Concepts – 9th Edition

Operating System Design and Implementation (Cont.)

(cid:0) Important principle to separate

Policy: What will be done? Mechanism: How to do it?

(cid:0) Mechanisms determine how to do something, policies decide

what will be done

(cid:0)

The separation of policy from mechanism is a very important principle, it allows maximum flexibility if policy decisions are to be changed later (example – timer)

(cid:0)

Specifying(x/định) and designing an OS is highly creative task of software engineering(kĩ thuật)

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2.33 Operating System Concepts – 9th Edition

Implementation

(cid:0) Much variation(sự biến đổi)

(cid:0) Early OSes in assembly language

(cid:0) Then system programming languages like Algol, PL/1

(cid:0) Now C, C++

(cid:0) Actually usually a mix of languages

(cid:0) Lowest levels in assembly

(cid:0) Main body in C (cid:0) Systems programs in C, C++, scripting languages like PERL,

Python, shell scripts

(cid:0) More high-level language easier to port to other hardware

(cid:0) But slower

(cid:0)

Emulation(mô phỏng) can allow an OS to run on non-native hardware

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2.34 Operating System Concepts – 9th Edition

Operating System Structure

(cid:0) General-purpose OS is very large program

(cid:0)

Various ways to structure ones (cid:0) Simple structure – MS-DOS (cid:0) More complex -- UNIX

(cid:0) Layered – an abstraction

(cid:0) Microkernel -Mach

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2.35 Operating System Concepts – 9th Edition

Simple Structure -- MS-DOS

(cid:0) MS-DOS – written to provide the most functionality(ch/năng) in the least space (cid:0) Not divided into modules (cid:0) Although MS-DOS has some structure, its interfaces and levels of functionality are not well separated

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2.36 Operating System Concepts – 9th Edition

Non Simple Structure -- UNIX

UNIX – limited by hardware functionality, the original UNIX operating system had limited structuring. The UNIX OS consists(b/gồm) of two separable parts (cid:0) Systems programs

(cid:0)

The kernel  Consists of everything below the system-call interface

and above(ở trên) the physical hardware

 Provides the file system, CPU scheduling, memory

management, and other operating-system functions; a large number of functions for one level

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2.37 Operating System Concepts – 9th Edition

Traditional UNIX System Structure

ượ Beyond(v t ra ngoài) simple but not fully layered

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2.38 Operating System Concepts – 9th Edition

Layered Approach

(cid:0)

The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.

(cid:0) With modularity, layers are

selected such that each uses functions (operations) and services of only lower-level layers

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2.39 Operating System Concepts – 9th Edition

Microkernel System Structure

(cid:0) Moves as much from the kernel into user space (cid:0) Mach example of microkernel

(cid:0) Mac OS X kernel (Darwin) partly based on Mach

(cid:0)

Communication takes place between user modules(đ/vị) using message passing

(cid:0)

Benefits(lợi ích): (cid:0) Easier to extend a microkernel (cid:0) Easier to port the operating system to new architectures (cid:0) More reliable (less code is running in kernel mode) (cid:0) More secure Detriments(thiệt hại): (cid:0) Performance overhead(tổng phí) of user space to kernel

space communication

2.40 Operating System Concepts – 9th Edition

Microkernel System Structure

Application Program

File System

Device Driver

user mode

messages

CPU scheduling

memory managment

Interprocess Communication

kernel mode

microkernel

hardware

2.41 Operating System Concepts – 9th Edition

Modules

(cid:0) Many modern operating systems implement loadable kernel

modules (cid:0) Uses object-oriented approach(p/pháp) (cid:0) Each core component is separate (cid:0) Each talks to the others over known interfaces (cid:0) Each is loadable as needed within the kernel (cid:0) Overall, similar to layers but with more flexible(linh hoạt)

(cid:0) Linux, Solaris, etc

2.42 Operating System Concepts – 9th Edition

Solaris Modular Approach

2.43 Operating System Concepts – 9th Edition

Hybrid Systems

(cid:0) Most modern operating systems are actually not one pure(thuaafn

tuý) model (cid:0) Hybrid(hỗn tạp) combines(phối hợp) multiple(nhiều)

approaches(gần như, xấp xỉ) to address performance, security, usability(dùng đc) needs

(cid:0)

Linux and Solaris kernels in kernel address space, so monolithic(ng/khối), plus modular for dynamic(động) loading of functionality

(cid:0) Windows mostly monolithic, plus microkernel for different

subsystem personalities

(cid:0)

Apple Mac OS X hybrid, layered, Aqua UI plus Cocoa programming environment (cid:0) Below is kernel consisting of Mach microkernel and BSD Unix parts, plus I/O kit and dynamically loadable modules (called kernel extensions)

2.44 Operating System Concepts – 9th Edition

Mac OS X Structure

graphical user interface

Aqua

application environments and services

Java

Cocoa

Quicktime

BSD

kernel environment

BSD

Mach

I/O kit

kernel extensions

2.45 Operating System Concepts – 9th Edition

iOS

(cid:0)

Apple mobile OS for iPhone, iPad (cid:0) Structured on Mac OS X, added functionality (cid:0) Does not run OS X applications natively

 Also runs on different CPU architecture

(ARM vs. Intel)

(cid:0) Cocoa Touch Objective-C API for

developing apps

(cid:0) Media services layer for graphics, audio,

video

(cid:0) Core services provides cloud computing,

databases

(cid:0) Core operating system, based on Mac OS X

kernel

2.46 Operating System Concepts – 9th Edition

Android

(cid:0)

(cid:0) Developed by Open Handset Alliance (mostly Google) (cid:0) Open Source Similar stack to IOS

(cid:0)

Based on Linux kernel but modified (cid:0) Provides process, memory, device-driver management (cid:0) Adds power management Runtime environment includes core set of libraries and Dalvik virtual machine (cid:0) Apps developed in Java plus Android API

 Java class files compiled to Java bytecode then translated

to executable than runs in Dalvik VM

(cid:0)

Libraries include frameworks for web browser (webkit), database (SQLite), multimedia, smaller libc

2.47 Operating System Concepts – 9th Edition

Android Architecture Applications

Application Framework

Libraries

Android runtime

SQLite

openGL

Core Libraries

surface manager

media framework

Dalvik virtual machine

webkit

libc

Linux kernel

2.48 Operating System Concepts – 9th Edition

Operating-System Debugging

(cid:0)

Debugging is finding and fixing errors, or bugs (cid:0) OS generate log files containing error information

(cid:0)

Failure of an application can generate core dump file capturing memory of the process

(cid:0) Operating system failure can generate crash(đổ vỡ, k/thúc ko bình

thường) dump(câm) file containing kernel memory

(cid:0)

Beyond crashes, performance tuning(điều chỉnh) can optimize(tối ưu hoá) system performance (cid:0) Sometimes using trace(dấu vết) listings of activities, recorded for

analysis(p/tích)

(cid:0) Profiling(định hình) is periodic(c/kỳ) sampling of instruction pointer to look for statistical(thống kê) trends(xu hướng)

Kernighan’s Law: “Debugging is twice as hard as writing the code in the

first place. Therefore, if you write the code as cleverly as(khôn ngoan) possible, you are, by definition, not smart enough to debug it.”

2.49 Operating System Concepts – 9th Edition

Performance Tuning

(cid:0)

Improve performance by removing bottlenecks(tắc nghẽn)

(cid:0) OS must provide means of computing and displaying measures of system behavior

(cid:0)

For example, “top” program or Windows Task Manager

2.50 Operating System Concepts – 9th Edition

DTrace

(cid:0)

DTrace tool in Solaris, FreeBSD, Mac OS X allows live instrumentation on production systems

(cid:0)

Probes fire when code is executed within a provider, capturing state data and sending it to consumers of those probes

(cid:0)

Example of following XEventsQueued system call move from libc library to kernel and back

2.51 Operating System Concepts – 9th Edition

Dtrace (Cont.)

(cid:0)

Dtrace(vết) code to record amount(lượng) of time each process with UserID 101 is in running mode (on CPU) in nanoseconds

2.52 Operating System Concepts – 9th Edition

Operating System Generation

(cid:0) Operating systems are designed to run on any of a class of

machines; the system must be configured(cấu hình) for each specific computer site

(cid:0)

SYSGEN program obtains(thu đc) information concerning(liên quan) the specific configuration of the hardware system (cid:0) Used to build system-specific compiled kernel or system-

tuned

(cid:0) Can general more efficient code than one general kernel

2.53 Operating System Concepts – 9th Edition

System Boot

(cid:0) When power initialized(khởi chạy) on system, execution starts at a

fixed memory location

(cid:0) Firmware ROM used to hold initial boot code

(cid:0) Operating system must be made available to hardware so hardware

can start it (cid:0) Small piece of code – bootstrap loader, stored in ROM or

EEPROM locates the kernel, loads it into memory, and starts it (cid:0) Sometimes two-step process where boot block at fixed location loaded by ROM code, which loads bootstrap loader from disk

(cid:0)

Common bootstrap loader, GRUB, allows selection of kernel from multiple disks, versions, kernel options