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Support for a wide range of drivers and easy insertion of a new driver in the system Benefits of I / O subsystem any universal OS is a different set of drivers for the most popular peripheral devices. Well-planned and implemented operating system may fail in the market only because it did not include an adequate set of drivers and administrators and users have to go right for them to the driver of their external device to equipment manufacturers, or worse, with its development. It was in such a situation were people first version of OS / 2, and perhaps this is a time not for the last delivery positions that good operating system, drivers are rich in Windows 3.x. To operating system is not a lack of experienced drivers, it is necessary to have a clear, friendly and open interface between drivers and other parts of the OS. This interface is used to ensure that drivers are not only wrote directly developers of the operating system, but also a large army of programmers around the world, especially those businesses that produce external devices for computers. Openness interface drivers, that is his description of the accessibility to independent software developers (and perhaps also to develop it by conciliation between the leading teams of developers), is a prerequisite for successful development of the operating system. The driver works on the one hand, with the OS kernel modules (modules, I / O subsystems, modules, system calls, modules and subsystems management of memory, etc.), on the other hand, with controllers external devices. So there are two types of interfaces: "EibConnection kernel interface" (Driver Kernel Interface, DKI), and interface "device" EibConnection (Device Driver Interface, DDF). "EibConnection kernel interface" should be standardised in any case, a "EibConnection interface device" makes sense to standardize when the subsystem I / O driver is not permitted to interact directly with the hardware controller, and carry out these operations on their own. Escaping driver of the equipment is very useful function, as well as driver in this case is independent of the hardware platform. I / O subsystem can support several different types of interfaces DKI / DDI, providing specific interface devices for a certain class. For example, Windows NT drivers for the Network Adapter is the interface standard NDIS (Network Driver Interface Specification), while drivers of network transport protocols interact with the upper layers of network software interface for TDI (Transport Driver Interface). Usually I / O subsystem supports a large number of system functions that can cause a driver to perform some action model. Examples can be referred to an exchange transaction registers controller, a buffer for interim storage I / O synchronization of several drivers, copying data from user space to space systems, etc. To support the development of drivers operating system typically issued a so-called package DDK (Driver Development Kit), a set of tools, libraries, compilers and otladchikov. Dynamic loading and unloading of drivers Suggest a better translation Thank you for contributing your translation suggestion to Google Translate. We'll use your suggestion to improve translation quality in future updates to our system. I found and file system One of the main tasks OS is the exchange of data between applications and computer peripheral devices. In order to achieve this, and have developed the first system programs, which have prototypes operating systems. In modern OS features data exchange with peripheral devices perform I / O subsystem. Clients of the subsystem are both users and applications, but also some components of the operating system, which requires the system data or withdrawal of such facility management processes in the active process of change must be written to the drive context priostanavlivaemogo process and take from the disk context aktiviziruemogo process. The main components are the I / O subsystem drivers that control external devices, and file system. For I / O subsystem is also with some conventions include the controller and interrupt considered above. Conditionality is * interrupt controller that serves not only the I / O subsystem modules, and other modules operating system, in particular an important module, as planner / flow controller. But because the planning subsystem I / O represents a major proportion of the burden off the controller, it is logical to consider it as part of (the same root of the emergence of computer systems were off at the time of operation with I / O devices) . File system because of its complexity, specificity and importance as a major repository of all information computer system should be considered in a separate chapter. However, the file is viewed in conjunction with other components of I / O subsystem for two reasons. First, the file system makes extensive use of the remaining parts of I / O subsystem, and secondly, the model file is the basis of most of access to devices used in modern I / O subsystem. Objectives of the OS files and devices Input / Output Subsystem (Input-Output Subsystem) multiprogrammnoy OS in the exchange of data with external computer devices must address some common challenges, of which the most important are: organization of parallel I / O devices and the processor; Harmonization of the exchange rate and data caching; separation devices and data between processes; Providing convenient logical interface between devices and the rest of the system; supporting a wide range of drivers with the simple inclusion of a new driver; dynamic loading and unloading of drivers; Support multiple file systems; supporting synchronous and asynchronous I / O operations. The following topics are dealt with in detail these challenges. The organization of parallel I / O devices and the processor Each device I / O-drive computer system, printer, terminal, etc.-equipped special unit, called the controller. The controller works with driver-system software module designed to manage the appliance. The controller periodically takes from the driver output device information, as well as team management, which suggests that this information needs to be done (for example, put a text in a certain area of the terminal or write in a certain sector of the disk). Under the management controller device may some time to carry out its operations autonomously, without the need for attention from the CPU. This time depends on many factors - volume output, in the Purple manager device controller, device speed, etc. Even the most primitive controller that performs simple functions, usually spends a lot of time on self-realization of such functions after regular command processor. The same is true for complex controllers, as well as the speed of any I / O device, even the speed is usually considerably lower than the speed of the processor. The processes taking place in the controller, occur between Cards teams regardless of OS. From the I / O subsystem is required to plan in real time (which operate external devices) and the suspension of running a large number of different drivers, ensuring an acceptable response time for each driver to an event controller. On the other hand, it is necessary to minimize the load processor I / O tasks, leaving as much processing time to implement user flows. This is a classic challenge to the planning and real-time systems are usually decided on the basis of a multi-priority scheme for discontinuing service. To ensure an acceptable level of response all drivers (or part of the drivers) are several levels of priority in accordance with the requirements of time and reaction time of the processor. To implement priority schemes usually operate general manager interruption OS. Harmonization of speed and cache data exchange When data is always a challenge to harmonize speed. For example, if one user process produces some of the data and transmit them to another user through the process of RAM, in general, the speed of data generation and reading do not match. Harmonization speed is usually achieved by buffering data in RAM and synchronization of processes to access the buffer. In the I / O subsystem to coordinate the exchange rate is also commonly used data buffering in memory. In those specialized operating systems, which provide high-speed I / O is a priority (Real-time services network file services, etc.), much of RAM are not under the code of applications, and by buffering data. But buffering only on the basis of RAM in the I / O subsystem is not is the difference between the exchange rate and operational memory, which processes data processing facilities, and the speed of external devices often too large to a temporary buffer could be operational memory-volume may simply not enough. For such cases should be special measures, and is often used as a buffer disk file, also called spul- file (from the spool - spool, the same buffer, only to train). A typical example of an organization spulinga output to the printer. To print documents in dozens of megabytes is not unusual, therefore, for temporary storage (and print any document takes a few minutes to tens of minutes) of RAM is not enough. Another solution to this problem is to use a large buffer memory controllers external devices. This approach is especially useful when placing data on disk too slow exchange (or the data displayed on the disc itself). For example, the graphics display controllers used buffer memory, commensurate with the volume of operational, and it has accelerated withdrawal schedules on the screen. Buffering data not only agree on the speed of the processor and external devices, but also to other tasks, reduce the number of actual I / O operations through data caching. The disk cache is a feature I / O subsystems virtually all operating systems, significantly reducing time access to the stored data. Sharing devices and data between processes I / O devices can be processes in a monopoly, and the joint use of (shared). This OS should provide access control by the same means as in access to other resources of computer systems by testing a user or group of users on whose behalf a process to carry out an operation of the device. For example, a particular group of users allowed to capture the serial port of monopoly ownership, and other users is prohibited. The operating system can control access not only to the device as a whole, but to individual portion of data stored or displayed this device. The disc is a typical example of the device for which it is important to control access to the device is not as a whole and to individual directories and files. In finding information on graphic display windows of the screen are also a resource, which must be a kind of ongoing access to the system processes. It is for each portion of the device or data may be put to the right, not directly connected with access to the device as a whole. For example, the file system, usually for each directory and file can be set individual access rights. Obviously, joint access to parts of the device or the data stored on it, a prerequisite for the job is a shared device as a whole. The same device in different time periods can be used as shared, and monopoly regimes. Nevertheless, there are devices, which are usually characterized by one of these regimes, such as sequential alphanumeric ports and terminals are used in the monopoly regime, and drive-line sharing. The operating system should provide the devices in both modes, providing tracking procedures capture and release devices used monopoly, in the case of sharing of optimizing the sequence of I / O operations for the various processes to improve overall productivity, if possible. For example, data from several processes disc can be streamlined so the sequence of operations that unproductive time on the movement of heads significantly reduced (although for some of the processes may slow I / O operations). In the division between devices may be needed in distinguishing portion of the two processes from each other. Normally such a need arises to share the so-called serial devices, data which, unlike direct access devices not addressed. Typical representatives of such devices is a printer that is not allocated in the possession of monopoly power, and at the same time each document will be published as a coherent set of pages. For these devices is organized mainly by finding jobs, each job is a portion of data that can break, such as paper for printing. To keep jobs queue used spul- file, which both agree on the speed of the printer and memory and provides logical segmentation data portion. As spul- file is shared direct access devices, the processes can simultaneously output to the printer, placing data in its section spul- file. Providing convenient logical interface between devices and the rest of the system Variety of I / O devices made especially urgent as a masking OS logical interface between peripheral devices and applications. Virtually all modern operating systems support as a basis for such an interface file model of peripheral devices when any device looks for a consistent set of application programmer bytes, which is working with the unified system calls (for example, read and write), asking the name of the device and the debug output log file shifting from the start byte. To sustain such an interface I / O subsystem lot of work to be done, given the difference in data operations, such as the hard disk and graphics terminal. The attractiveness of the model debug output log file device is its simplicity and uniformity to the devices of any kind, but in many cases for programming some of Input / Output devices, it is too poor. Therefore, the model is often used as the only basis on which I / O subsystem builds more content model device type. I / O subsystem provides, as a rule, a specific interface to display graphical information on the screen or printer, for programming operations networking, etc. This specific interface developer can always build on the existing base interface. Support for a wide range of drivers and easy insertion of a new driver in the system Benefits of I / O subsystem any universal OS is a different set of drivers for the most popular peripheral devices. Well-planned and implemented operating system may fail in the market only because it did not include an adequate set of drivers and administrators and users have to go right for them to the driver of their external device to equipment manufacturers, or worse, with its development. It was in such a situation were people first version of OS / 2, and perhaps this is a time not for the last delivery positions that good operating system, drivers are rich in Windows 3.x. To operating system is not a lack of experienced drivers, it is necessary to have a clear, friendly and open interface between drivers and other parts of the OS. This interface is used to ensure that drivers are not only wrote directly developers of the operating system, but also a large army of programmers around the world, especially those businesses that produce external devices for computers. Openness interface drivers, that is his description of the accessibility to independent software developers (and perhaps also to develop it by conciliation between the leading teams of developers), is a prerequisite for successful development of the operating system. The driver works on the one hand, with the OS kernel modules (modules, I / O subsystems, modules, system calls, modules and subsystems management of memory, etc.), on the other hand, with controllers external devices. So there are two types of interfaces: "EibConnection kernel interface" (Driver Kernel Interface, DKI), and interface "device" EibConnection (Device Driver Interface, DDF). "EibConnection kernel interface" should be standardised in any case, a "EibConnection interface device" makes sense to standardize when the subsystem I / O driver is not permitted to interact directly with the hardware controller, and carry out these operations on their own. Escaping driver of the equipment is very useful function, as well as driver in this case is independent of the hardware platform. I / O subsystem can support several different types of interfaces DKI / DDI, providing specific interface devices for a certain class. For example, Windows NT drivers for the Network Adapter is the interface standard NDIS (Network Driver Interface Specification), while drivers of network transport protocols interact with the upper layers of network software interface for TDI (Transport Driver Interface). Usually I / O subsystem supports a large number of system functions that can cause a driver to perform some action model. Examples can be referred to an exchange transaction registers controller, a buffer for interim storage I / O synchronization of several drivers, copying data from user space to space systems, etc. To support the development of drivers operating system typically issued a so-called package DDK (Driver Development Kit), a set of tools, libraries, compilers and otladchikov. Dynamic loading and unloading of drivers It concerns the development of new drivers, there is also the problem of driver modules running in the OS, that is dynamic zagruzki- unloading the driver.
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