Browse Prior Art Database

Transient Device Ownership

IP.com Disclosure Number: IPCOM000040289D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Earnst, R: AUTHOR [+2]

Abstract

This article describes a method for assigning input/output devices to processes in such a fashion as to optimize the operating system overhead required to process input/output data for the device. Device assignment is determined according to the I/O interrupt frequency rate for the device. By allowing such allocation of devices, the system overhead for processing input and output for the device is reduced. In an operating system it is possible to require that I/O peripheral devices are privately owned and exclusively used by processes. It is also possible that multiple application processes may attempt to use such a privately owned device, creating a substantial amount of contention for such an assigned device.

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Transient Device Ownership

This article describes a method for assigning input/output devices to processes in such a fashion as to optimize the operating system overhead required to process input/output data for the device. Device assignment is determined according to the I/O interrupt frequency rate for the device. By allowing such allocation of devices, the system overhead for processing input and output for the device is reduced. In an operating system it is possible to require that I/O peripheral devices are privately owned and exclusively used by processes. It is also possible that multiple application processes may attempt to use such a privately owned device, creating a substantial amount of contention for such an assigned device. When multiple processes must read and write the device, each non-device owning process must depend on the owning process to manage the input/output for the device on behalf of the requesting process.

When such requests occur at a very high rate of frequency, the impact on the overall performance of the entire system can be substantial.

An example of how such a scenario can occur is UNIX* "raw mode". "Raw mode" is a generic name for processing terminal I/O in a character mode. In such a mode, every character of input is directly passed to and processed by the requesting process before the next character is read and each character is written to the device one at a time for output. Such modes of operation are standard for applications such as full-screen editors and command processors. According to the new method of Transient Device Ownership, the previously unnecessary processing required for I/O is eliminated. The ...