Transfer spooling technology--operating system

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Spooling technology--operating system

Spooling technology (simultaneous peripheral Operating on line)

At the same time, on-line peripheral operation Technology, it is about how the slow-speed character device and computer host data exchange of a technology, often referred to as spooling technology.

In the multi-channel program environment, using one or two programs in the multi-channel program to simulate the function of the peripheral controller in the offline input/output, in order to achieve "offline" input/output purposes.

This technology can be used to transform exclusive devices into shared virtual devices, thus increasing the utilization of exclusive devices and the speed of process advancement.

The spooling system is a simulation of the offline input/output operation, and it must have large-capacity, random-access memory
The support.

The main idea is to operate in two directions on the online condition, transfer data from the input device to disk or tape (block device) at data input, and then connect the block devices to the host, in turn, the output data is transferred to the disk or tape on the data output, and then transferred from the disk or tape to the output device.

This allows an exclusive physical device to be virtualized as a parallel-used polymorphic logical device, allowing the physical device to be shared by multiple processes.

The input process SPI is the peripheral controller that simulates the offline input, which sends the data requested by the user from the input device through the input buffer to the input well (an area on the disk), which is read into memory directly from the input well when the CPU processes the data.

The output process SPO is the peripheral controller that simulates the offline output, the data that the user requires to output is sent from memory to the output well, and when the output device is idle, the data in the output well is transmitted through the output buffer (an area in memory) to the output device.

Example--Printer sharing with printer

has been widely used in multi-user systems and computer networks, it is actually using spooling technology to transform the exclusive printer into a device for users to share, as long as there is enough external memory space and multi-channel program operating system support.

1. When a user process requests a printout, the spooling system immediately agrees to print out the process, but does not actually assign the printer to the user process, but only two things for the process: one is to request an idle storage space for the output process SPO in the output well, And the data to be printed is transferred and stored; Another task is to request a blank user request print table for the user process by the output process SPO, and fill in the user's print request, and then hang the table on the printer's request queue. At this point, if there is another process requesting the printer, the system still agrees to print out the process, and of course the work done by the system is still the above two things.

2, when the printer is performing the actual printing, if the printer is idle, the output process SPO will take out a print table from the team that requested the print queue, transfer the data from the output well to the memory output buffer, and then transfer it to the printer to print according to the requirements in the printed table. After printing, the output process SPO will then check whether the request print queue still needs to print the request table, if any, then take out a request to print the table, the new but the requirements continue to print. So again and again, until the print queue is requested to be empty, the output process blocks itself and wakes up the next time a print request is requested.

Transfer spooling technology--operating system