![Page 1: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/1.jpg)
Ridge Xu13.1Operating System Concepts
Chapter 13: I/O Systems
I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to Hardware Operations Streams Performance
![Page 2: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/2.jpg)
Ridge Xu13.2Operating System Concepts
I/O Hardware
Incredible variety of I/O devices Common concepts
Port Bus (daisy chain or shared direct access)Controller (host adapter)
I/O instructions control devices Devices have addresses, used by
Direct I/O instructionsMemory-mapped I/O
![Page 3: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/3.jpg)
Ridge Xu13.3Operating System Concepts
A Typical PC Bus Structure
![Page 4: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/4.jpg)
Ridge Xu13.4Operating System Concepts
Device I/O Port Locations on PCs (partial)
![Page 5: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/5.jpg)
Ridge Xu13.5Operating System Concepts
Polling
Determines state of device command-ready busy Error
Busy-wait cycle to wait for I/O from device
![Page 6: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/6.jpg)
Ridge Xu13.6Operating System Concepts
Interrupts
CPU Interrupt request line triggered by I/O device
Interrupt handler receives interrupts
Maskable to ignore or delay some interrupts
Interrupt vector to dispatch interrupt to correct handlerBased on prioritySome unmaskable
Interrupt mechanism also used for exceptions
![Page 7: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/7.jpg)
Ridge Xu13.7Operating System Concepts
Interrupt-Driven I/O Cycle
![Page 8: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/8.jpg)
Ridge Xu13.8Operating System Concepts
Intel Pentium Processor Event-Vector Table
![Page 9: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/9.jpg)
Ridge Xu13.9Operating System Concepts
Direct Memory Access
Used to avoid programmed I/O for large data movement
Requires DMA controller
Bypasses CPU to transfer data directly between I/O device and memory
![Page 10: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/10.jpg)
Ridge Xu13.10Operating System Concepts
Six Step Process to Perform DMA Transfer
![Page 11: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/11.jpg)
Ridge Xu13.11Operating System Concepts
Application I/O Interface
I/O system calls encapsulate device behaviors in generic classes
Device-driver layer hides differences among I/O controllers from kernel
Devices vary in many dimensionsCharacter-stream or blockSequential or random-accessSharable or dedicatedSpeed of operation read-write, read only, or write only
![Page 12: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/12.jpg)
Ridge Xu13.12Operating System Concepts
A Kernel I/O Structure
![Page 13: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/13.jpg)
Ridge Xu13.13Operating System Concepts
Characteristics of I/O Devices
![Page 14: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/14.jpg)
Ridge Xu13.14Operating System Concepts
Block and Character Devices
Block devices include disk drivesCommands include read, write, seek Raw I/O or file-system accessMemory-mapped file access possible
Character devices include keyboards, mice, serial portsCommands include get, put Libraries layered on top allow line editing
![Page 15: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/15.jpg)
Ridge Xu13.15Operating System Concepts
Network Devices
Varying enough from block and character to have own interface
Unix and Windows NT/9i/2000 include socket interfaceSeparates network protocol from network operation Includes select functionality
Approaches vary widely (pipes, FIFOs, streams, queues, mailboxes)
![Page 16: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/16.jpg)
Ridge Xu13.16Operating System Concepts
Clocks and Timers
Provide current time, elapsed time, timer
If programmable interval time used for timings, periodic interrupts
ioctl (on UNIX) covers odd aspects of I/O such as clocks and timers
![Page 17: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/17.jpg)
Ridge Xu13.17Operating System Concepts
Blocking and Nonblocking I/O
Blocking - process suspended until I/O completedEasy to use and understand Insufficient for some needs
Nonblocking - I/O call returns as much as availableUser interface, data copy (buffered I/O) Implemented via multi-threadingReturns quickly with count of bytes read or written
Asynchronous - process runs while I/O executesDifficult to use I/O subsystem signals process when I/O completed
![Page 18: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/18.jpg)
Ridge Xu13.18Operating System Concepts
Kernel I/O Subsystem
SchedulingSome I/O request ordering via per-device queueSome OSs try fairness
Buffering - store data in memory while transferring between devices To cope with device speed mismatch To cope with device transfer size mismatch To maintain “copy semantics”
![Page 19: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/19.jpg)
Ridge Xu13.19Operating System Concepts
Sun Enterprise 6000 Device-Transfer Rates
![Page 20: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/20.jpg)
Ridge Xu13.20Operating System Concepts
Kernel I/O Subsystem
Caching - fast memory holding copy of dataAlways just a copyKey to performance
Spooling - hold output for a device If device can serve only one request at a time i.e., Printing
Device reservation - provides exclusive access to a deviceSystem calls for allocation and deallocationWatch out for deadlock
![Page 21: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/21.jpg)
Ridge Xu13.21Operating System Concepts
Error Handling
OS can recover from disk read, device unavailable, transient write failures
Most return an error number or code when I/O request fails
System error logs hold problem reports
![Page 22: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/22.jpg)
Ridge Xu13.22Operating System Concepts
Kernel Data Structures
Kernel keeps state info for I/O components, including open file tables, network connections, character device state
Many, many complex data structures to track buffers, memory allocation, “dirty” blocks
Some use object-oriented methods and message passing to implement I/O
![Page 23: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/23.jpg)
Ridge Xu13.23Operating System Concepts
UNIX I/O Kernel Structure
![Page 24: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/24.jpg)
Ridge Xu13.24Operating System Concepts
I/O Requests to Hardware Operations
Consider reading a file from disk for a process: Determine device holding file Translate name to device representationPhysically read data from disk into bufferMake data available to requesting processReturn control to process
![Page 25: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/25.jpg)
Ridge Xu13.25Operating System Concepts
Life Cycle of An I/O Request
![Page 26: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/26.jpg)
Ridge Xu13.26Operating System Concepts
STREAMS
STREAM – a full-duplex communication channel between a user-level process and a device
A STREAM consists of:
- STREAM head interfaces with the user process
- driver end interfaces with the device- zero or more STREAM modules between them.
Each module contains a read queue and a write queue
Message passing is used to communicate between queues
![Page 27: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/27.jpg)
Ridge Xu13.27Operating System Concepts
The STREAMS Structure
![Page 28: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/28.jpg)
Ridge Xu13.28Operating System Concepts
Performance
I/O a major factor in system performance:
Demands CPU to execute device driver, kernel I/O codeContext switches due to interruptsData copyingNetwork traffic especially stressful
![Page 29: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/29.jpg)
Ridge Xu13.29Operating System Concepts
Intercomputer Communications
![Page 30: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/30.jpg)
Ridge Xu13.30Operating System Concepts
Improving Performance
Reduce number of context switches Reduce data copying Reduce interrupts by using large transfers, smart controllers,
polling Use DMA Balance CPU, memory, bus, and I/O performance for highest
throughput
![Page 31: Ridge Xu 13.1 Operating System Concepts Chapter 13: I/O Systems I/O Hardware Application I/O Interface Kernel I/O Subsystem Transforming I/O Requests to](https://reader035.vdocuments.site/reader035/viewer/2022070305/551425c8550346ec488b5a3d/html5/thumbnails/31.jpg)
Ridge Xu13.31Operating System Concepts
Device-Functionality Progression