Chp 1 Introduction

tags: 作業系統

• Chp 1 Introduction
  • Operation System
  • Program, Proccese, Thread
  • Interrupt
  • I/O Structure
  • Storage
  • Computer-System Architecture
  • Dual-Mode
  • Network
  • Virtualization

Operation System

• Computer Structure

“The one program running at all times on the computer” is the kernel.

Program, Proccese, Thread

Ref: Program/Process/Thread 差異

• Program: 還尚未load入記憶體的 code (工廠藍圖)

  • 相同 Program 的 Process 可以多個同時存在
  • Passive Entity

• Process: 已經執行並且 load 到記憶體中的 Program (運作之工廠)

  • Active Entity
  • Process 是電腦中已執行 Program 的實體
  • 一個 CPU 一次只能執行一個 Process，每一個 Process 互相獨立
  • Process 的運行量總量不會少於 CPU 的總量

• Thread: Process 是 Thread 的容器 (工廠工人)

  • 同一個 Process 可以同時存在多個 Thread
  • 同一個 Process 底下的 Thread 共享資源，不同的Process 則否
  • 兩個以上執行緒若同時存取或改變全域變數(Global Variable)，則可能發生同步(Synchronization，恐龍本第六章)問題。
  • 若執行緒之間互搶資源，則可能產生死結(Deadlock，恐龍本第七章)

不同的Process一樣可以共享資源，這可以藉由share memory或是message passing model達成，message passing model可以是socket或是其他的通訊方式
不管是thread或是process之間，要共享資源就要解決互搶資源的現象，如同Thread第3,4點所述，解決的方式可以藉由添加互斥鎖，之後會教。
Neko

• program counter
  • specifying location of next instruction to execute
  • one program counter per thread

Interrupt

• Polling

  • Idle 時，固定隔一段時間從Queue檢查是否有interrupt

  說Queue好像有點怪怪的，但是總之就是固定去檢查裝置
  Neko

• vectored interrupt system

• vectored v.s. non-vectored interrupt

• Interrupt v.s Trap(or exception)

  • Interrupt
    • hardware-generated
  • Trap:
    • software-generated

I/O Structure

• System call

  • request to the OS to allow user to wait for I/O completion.

• Device-status table

  • 同時有很多I/O運作，儲存各個I/O狀態在此

Storage

• Storage Hierarchy
  • Speed
  • Cost
  • Volatility (need extra power to store the data)

• Main Memory

  • Random access
  • Volatile

• Caching

  • Copying information into faster storage system

• Direct Memory Access(DMA)

  • Transfers blocks of data from buffer storage directly to main memory without CPU.
  • Close to the memory speeds

Computer-System Architecture

• DEFINITION

  • Core — The basic computation unit of the CPU.
  • CPU — The hardware that executes instructions.
  • Processor — A physical chip that contains one or more CPUs.

• Multiprocessors

  • parallel systems, tightly-coupled systems
  • Types & Difference
    • Asymmetric Multiprocessor
      • Only Master processor run the tasks of OS
      • Master processor allocate work to slave processor
      • No-shared memory
    • Symmetric Multiprocessor
      • Each processor run the tasks in OS
      • shared memory

• Multi-chip, Multicores
  

• Multiprocessor VS Multicore

	Multicore	Multiprocessor
Definition	a single CPU with multiple execution unit	a system that has two or more CPUs
Advantage	execute single program faster	execute multiple program faster
Reliablility	not reliable	more reliable CPU won't affect the other

• Multiprogramming (Batch system)

  • organizes jobs to keep CPU executing
  • require job scheduling

• Timesharing (multitasking)

  • CPU switches jobs frequently to create interactive computing
  • require CPU scheduling

• Clustered Systems

  • multiple systems working together
  • parallelization required
  • distributed lock manager (DLM) avoid conflict operations
  • Type
    • Asymmetric
      • one machine in hot-standby mode
      • a hot standby node is part of the system . The hot standby node continuously monitors the server and if it fails, the hot standby node takes its place.
    • Symmetric
      • multiple nodes running, monitoring each other

Network 的概念？

Omnom

Dual-Mode

• Purpose: Allow OS to protect itself and other system components.
• user mode (mode bit=1) and kernel mode (mode bit=0)
• Some privileged instructions only excutable in kernel mode
  

Network

• Distributed Computing (TCP/IP)

  • Local Area Network (LAN)
  • Wide Area Network (WAN)
  • Metropolitan Area Network (MAN)
  • Personal Area Network (PAN)

• Client-Server

  • Compute-server: clients request services
  • File-server: clients store and retrieve files

• Peer-to-Peer

  • no distinguish clients and servers
  • Broadcast request via discovery protocol

Virtualization

Simulator and Emulator