tailieunhanh - Lecture Operating system concepts - Chapter 13: I/O systems

The role of the operating system in computer I/O is to manage and control I/O operations and I/O devices. Although related topics appear in other chapters, here we bring together the pieces to paint a complete picture of I/O. First, we describe the basics of I/O hardware. Next, we discuss the I/O services provided by the operating system and the embodiment of these services in the application I/O interface. Then, we explain how the operating system bridges the gap between the hardware interface and the application interface. | Chapter 13: I/O Systems I I/O Hardware I Application I/O Interface I Kernel I/O Subsystem I Transforming I/O Requests to Hardware Operations I Streams I Performance Operating System Concepts Silberschatz, Galvin and Gagne 2002 I/O Hardware I Incredible variety of I/O devices I Common concepts ✦ Port ✦ Bus (daisy chain or shared direct access) ✦ Controller (host adapter) I I/O instructions control devices I Devices have addresses, used by ✦ Direct I/O instructions ✦ Memory-mapped I/O Operating System Concepts Silberschatz, Galvin and Gagne 2002 A Typical PC Bus Structure Operating System Concepts Silberschatz, Galvin and Gagne 2002 Device I/O Port Locations on PCs (partial) Operating System Concepts Silberschatz, Galvin and Gagne 2002 Polling I Determines state of device ✦ command-ready ✦ busy ✦ Error I Busy-wait cycle to wait for I/O from device Operating System Concepts Silberschatz, Galvin and Gagne 2002 Interrupts I CPU Interrupt request line triggered by I/O device I Interrupt handler receives interrupts I Maskable to ignore or delay some interrupts I Interrupt vector to dispatch interrupt to correct handler ✦ Based on priority ✦ Some unmaskable I Interrupt mechanism also used for exceptions Operating System Concepts Silberschatz, Galvin and Gagne 2002 Interrupt-Driven I/O Cycle Operating System Concepts Silberschatz, Galvin and Gagne 2002 Intel Pentium Processor Event-Vector Table Operating System Concepts Silberschatz, Galvin and Gagne 2002 Direct Memory Access I Used to avoid programmed I/O for large data movement I Requires DMA controller I Bypasses CPU to transfer data directly between I/O device and memory Operating System Concepts Silberschatz, Galvin and Gagne 2002 Six Step Process to Perform DMA Transfer Operating System Concepts Silberschatz, Galvin and Gagne .