Fifth chapter: Input/Output (IO) management

I/O device concepts:

Refers to all the devices inside the computer except the central processor and memory, often referred to as external devices.

I/O device classifications:

• Classification by Interactive objects:

• Human-Computer Interaction equipment

• Devices that interact with computers or other electronic devices

• Co-signaling equipment between computers

• Classification by interactive direction:

• Input (readable)

• Output (writable)

• Input/output (readable and writable)

• Classification by peripheral characteristics:

• Use features

• Transmit Data rate

• Information Organization features

I/O control mode:

• Program Access control mode

• Interrupt control mode

· DMA mode (direct memory addressing mode): Data Handling in memory

• Channel mode (on behalf of: USB)

Target of I/O Software:

• Device independence: When visiting a device, you do not need to know how to operate the device in detail.

• Unified naming

Hierarchical structure of I/O:

• User Layer

• Independent layer of equipment

• Device driver Layer

• Middle Fault

• Hardware Layer

I/O Scheduling concepts:

Scheduling a set of requests is a good order to execute these requests.

The operating system maintains a request-to-column for each device to implement scheduling.

One way to improve computer efficiency for I/O core subsystems is to perform I/O operations scheduling, using techniques for memory or storage space on disk. such as buffering, fast caching, spooling.

Fast cache:

Fast Cache is a fast memory that preserves copies of data, and quick access to cached copies is more efficient than the original data access.

Cache:

A buffer is an area of memory that is used to store data that is sent between two devices or between devices and applications.

Three effects of using buffers:

• The speed difference between the producer and the consumer handling the data stream

• Coordinate devices with inconsistent data transfer sizes

• Copy semantics for application I/O

Buffer:

• Single buffer

• Double buffering

• Cyclic buffering

• Buffer pool

Device Assignment Overview:

• For an exclusive device process, you must first request an assignment and then be able to perform I/O transfer

• For shared devices and virtual devices, there is no need to consider allocation issues, and processes can be directly requested by the file system.

Principle of equipment allocation:

According to the characteristics of the device, user requirements and system configuration conditions to determine

How devices are allocated: Static allocation and dynamic allocation

Device allocation policy: First Request first allocation (FIFO), priority high first allocation

Spool Technology (spooling):

Transform a single-use device into a shared device

The composition of the spooling system:

• Input wells and output wells (present in external memory)

• Input buffers and output buffers (present in memory)

• Input process SP1 and output process SP0

Error handling

Suppose I am I/O device error should be handled by I/O

Fifth chapter: Input/Output (IO) management