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資訊系統原理

郭大維教授

臺灣大學資訊工程系

Contents

?Computer Systems Overview

?Operating Systems Concept

?UNIX

?Other System Services

?Unified Modeling Language

?UML Introduction

?System Development Process

?Use Cases, Class Diagrams, etc.

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Operating Systems Concept

?What is an operating system?

?Operating system architecture

?Process concept

?CPU scheduling

?Memory management

?File and I/O systems

?Networking

What is an operating system?

?What is an operating system?

?A package of software called OS!

Hardware Operating System Application Systems useruser user useruser user

user

Kernel interface to the hardware System call interface

* “Operating system concept”, Silberschatz and Galvin, Addison Wesley, pp. 3-5

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?A control program

?Control the execution of user programs

?Prevent errors/misuse

?An environment for efficient/ convenient usage of a computer system.

?A resource allocator

?CPU, memory space, file storage, I/O devices, shared code, data structures, etc.

?Terminology

?Multiprogramming

?CPU/job scheduling – short/mid/long-term

?Time-sharing

?Multiprogramming + CPU switching ~ interactivities

?Batch processing

?Job pool – with/without multiprogramming

?Spooling (Simultaneous Peripheral Operation On-Line)

?Printf -> buffer (memory/disks) -> printout at a printer.

?Card readers -> disks -> run process

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Operating Systems Concept

?What is an operating system?

?Operating system architecture

?Process concept

?CPU scheduling

?Memory management

?File and I/O systems

OS Architecture

terminal controller, terminals, physical memory, device controller, devices such as disks, memory, etc.

CPU scheduling, signal handling, virtual memory, paging, swapping,

file system, disk drivers, caching/buffering, etc.

Shells, compilers, X, application programs, etc.

UNIX Kernel interface

to the hardware System call interface

useruser user useruser user user

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OS Architecture

?What components/functionality it has?

?Process Management

?Creation/deletion/suspension/resumption of user/system processes

?A process is a program in execution.

?Process scheduling

?Mechanisms for process synchronization

?Interprocess communication mechanisms

?Memory Management

?Memory allocation/deallocation

?Paging/segmentation memory management

?File Management

?Creation/deletion of files/directories

?Mapping of files to secondary storage

?I/O Systems & Storage Management

?Hide the peculiarity of specific H/W devices from users

?Storage allocation and management

?Disk scheduling

?Networking

?Various networking service such as naming resolution

?Protection System

?CPU, Memory, I/O devices

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OS’s on Parallel/Distributed Systems

?Parallel Systems

?More than one processor in close communication, sharing of bus, clock, sometimes memory and peripheral devices –

tightly coupled systems!

?Symmetric/asymmetric operating systems.

?Distributed Systems

?More than one processor without sharing of memory or any clock – loosely coupled systems!

?Heterogeneous vs homogeneous systems!

Real-Time OS

?Why RTOS

?A convenient and reliable environment to develop time/safety-critical applications.

?Requirements – depending on applications!

?Predictability – Verifiability & interrupt latency

?Reliability - Strictness of Deadline Violations

?Reconfigurability - System Size and Functionality

?Efficiency of System Components - Time

Granularity, Threads, and Resource Management

?Variable Models of Task Communication - Characteristics of Applications

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?Roadmap

?Booting

?I/O Structure

?Storage Hierarchy

?etc

* “Operating system concept”, Silberschatz and Galvin, Addison Wesley, pp. 24-30, 35-37

Computer System Architecture

CPU

cache

memory controller

memory

disk controller printer

controller printer

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Booting

?Bootstrap program

?Initialize all aspect of the systems

?E.g., CPU registers, device controllers, memory, etc.

?Load OS, and Run it!

?Run init to initialize system services

?Start virtual memory, various daemons, login processes, etc.

I/O Structure

?Parallelism of CPU and I/O activities

?Interrupts

I/O device

Process running on a CPU executing

transferring idle

I/O request I/O request

done

Process execution _interrupt

Interrupt handler

return

Process execution

Save Return Trace!

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I/O Structure

Bottom Half Top Half processes User

Space OS

System call interface

system calls, e.g.

READ/WRITE device drivers

hardware

time

interrupt Interrupt handler

data transfer

* Parallelism of multiple process executions!

?? Could OS return control to the process sooner??

•Synchronous I/O, e.g., reads

•Asynchronous I/O, e.g., writes

I/O Structure

?Interrupt types:

?Software interrupts (traps)

?Signals, division-by-zero, etc.

?Hardware interrupts

?Service requests of I/O devices, etc.

?Servicing of interrupts

?Generic handler

?Interrupt vector (UNIX)

?Masks, Disabling, Enabling

Handler_a() {

… ..

} bits to mask interrupts

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I/O Structure

?Device Status Table

Printer 1 Status: idle Disk 1 Status: Busy

…..

File:XX Offset:yyy Size:zzz

File:KK Offset:iii Size:jjj

Process execution

Waiting for I/O completion

Synchronous behavior!

I/O Structure

? DMA (Direct Memory Access)

? Release CPU from handling excessive interrupts

? e.g., a high-speed device:

? 2us service / 4us

? Procedure, e.g., WRITE

1. Use device driver to set up the registers of the DMA controller.

2. DMA moves blocks of data between memory and its own buffers.

3. Transfer from its buffers to its devices 4. Interrupt the CPU

Until done

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Storage Hierarchy

* “Operating system concept”, Silberschatz and Galvin, Addison Wesley, pp. 24-30, 35-37

registers cache main memory

electronic disks (battery) + others, e.g. flash magnetic disks

optical disks tapes

tertiary storage systems

CPU can directly access them!

nonvolatile storage

removable media

* Media – disk, Device – disk drive, System – device + controller + software

I/O and Storage Systems

?Cost/bit vs Capacity/dollar vs volatility

?Device I/O

?Memory-Mapped I/O

?For devices with fast response time

?Program I/O (PIO)

?polling

?Interrupt-Driven I/O

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Storage Hierarchy

?Caching

?When an information is used and might be used again, it is cached at a faster storage system.

?Strategies at different levels?

?Buffering

?When an information is “pushed” out to a slower storage system, it is buffered at a faster system for later actions.

?Relationship with caching?

Storage Hierarchy

?Coherency and Consistency

?Vertical information flow

?“Horizontal” information flow

CPU

Memory disks

CPU Memory

disks

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Dual Mode Protection

?What is “dual mode”?

?User mode

?Kernel mode

?Privileged instructions, such as I/O, memory-setting related instructions

?Rationale

?Only execute privileged instructions at the kernel mode to protect errors and misuse!

?Requirement

?Hardware support

* “Operating system concept”, Silberschatz and Galvin, Addison Wesley, pp. 39

…

Add R3, R4 SYS 23 ADD R5, R4

…

SysCall() {

… . }

Booting - Revisiting

?Bootstrap program – Kernel and Single User Mode

?Initialize all aspect of the systems

?E.g., CPU registers, device controllers, memory, etc.

?Load OS, and Run it! – Kernel and Multi-User Mode

?Run init to initialize system services

?Start virtual memory, various daemons, login processes, etc.

?Shell Processes – User and Multi-User Mode

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I/O Structure Revisiting

Bottom Half Top Half process User

Mode Kernel Mode

System call interface

system calls, e.g.

READ/WRITE device drivers

hardware

time

interrupt Interrupt handler

data transfer

* A bit in PSW of CPU to distinguish user or privileged instructio ns!