Browse Prior Art Database

Scheduler for IO Operations

IP.com Disclosure Number: IPCOM000087607D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Destombes, F: AUTHOR [+2]

Abstract

In the system of the drawing, representative I/O devices 1 and 2 are connected to a processor which supplies processing time or other system resources (represented by arrowed lines from the processor) in response to requests from the I/O devices (which are represented by arrowed lines to the processor. In response to a request, particular resources of the processor are assigned to particular I/O devices by a program that is called a scheduler.

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Scheduler for IO Operations

In the system of the drawing, representative I/O devices 1 and 2 are connected to a processor which supplies processing time or other system resources (represented by arrowed lines from the processor) in response to requests from the I/O devices (which are represented by arrowed lines to the processor. In response to a request, particular resources of the processor are assigned to particular I/O devices by a program that is called a scheduler.

As legends on the arrowed lines for I/O device 1 represent, the processor responds to a request by giving the device a unit of processing time (or other resource time) that is equal to or greater than a value that is designated P and is established for each I/O device. This response occurs within a time interval that is designated D. The I/O device can make a subsequent request after a delay that is designated T. The processor has registers that hold the selected values of P, D and T for each I/O device. These components of the system of the drawing are conventional.

In the system of the drawing, I/O device scheduling is further controlled according to a parameter C that designates a class of I/O device. I/O devices that are assigned to a first class are guaranteed predetermined values of P, D and T, as has been described. An example of an I/O device in this class is a magnetic tape unit; if the selected values of P, D and T are not provided, the tape unit may have an overrun which is costly to c...