文档介绍：Module 12: I/O Systems(I/O系统)
I/O hardwared(I/O硬件)
Application I/O Interface(应用程序I/O接口)
Kernel I/O Subsystem(核心I/O子系统)
Transforming I/O Requests to Hardware Operations
(转换I/O请求为硬件操作)
Performance(性能)
Applied Operating System Concepts
I/O Hardware(I/O硬件)
Incredible variety of I/O devices(难以置信的I/O设备种类)
Common concepts(基本概念)
Port (端口)
Bus (daisy chain or shared direct access)
(总线:菊花链或者共享总线)
Controller (host adapter)(控制器,主机适配器)
I/O instructions control devices(I/O指令控制设备)
Devices have addresses, used by (设备的寻址方式)
Direct I/O instructions(直接I/O指令)
Memory-mapped I/O(存储器映射I/O指令)
Applied Operating System Concepts
Polling(轮询)
Determines state of device (决定设备的状态)
command-ready(等待命令)
Busy(忙)
Error(错误)
Busy-wait cycle to wait for I/O from device
(忙等待循环等待设备的I/O操作)
Applied Operating System Concepts
Interrupts(中断)
CPU Interrupt request line triggered by I/O device
(CPU的中断需要有I/O设备的触发)
Interrupt handler receives interrupts
(中断处理例程接收中断)
Maskable to ignore or delay some interrupts
(通过屏蔽来忽略或者延迟某些中断)
Interrupt vector to dispatch interrupt to correct handler
(中断向量给中断分配正确的中断处理例程)
Based on priority(以优先级为基础)
Some unmaskable(某些中断不可屏蔽)
Interrupt mechanism also used for exceptions
(中断机制也用在异常)
Applied Operating System Concepts
Interrupt-drive I/O Cycle(中断驱动的I/O循环)
Applied Operating System Concepts
Direct Memory Access(直接内存存取)
Used to avoid programmed I/O for large data movement
(用来避免编程I/O来传输大量的数据)
Requires DMA controller(需要DMA控制器)
Bypasses CPU to transfer data directly between I/O device and memory (绕过CPU来在I/O设备和内存之间直接传输数据)
Applied Operating System Concepts
Six step process to perform DMA transfer (通过六步来完成DMA传输)
Applied Operating System Concepts
Application I/O Interface(应用程序I/O接口)
I/O system calls encapsulate device behaviors in generic classes
(I/O子系统设备行为精简成几个常用的类别)
Device-driver layer hides differences among I/O controllers from kernel(设备驱动层对核心隐藏了I/O控制器的不同细节)
Devices vary in many dimensions(设备变化范围非常大)
Character-stream or block(字符流或者块设备)
Sequential or random-access