1 I/O Hardware and I/O control methods Polling (轮询方式) Interrupts (中断方式) Direct Memory Access (DMA方式) I/O hardware summary 2 Application I/O Interface Block and Character Devices Network Devices Clocks and Timers Blocking (阻塞) and Nonblocking (非阻塞) I/O 3 Kernel I/O Subsystem I/O Scheduling Buffering (缓冲机制) Caching, Spooling & device reservation Error Handling I/O Protection Kernel Data Structures 4 Transforming I/O Requests to Hardware Operations 5 Performance