Browse Prior Art Database

Input/Output Queuing for Logically Sequential I/O in a Paging System

IP.com Disclosure Number: IPCOM000062353D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Duvall, KE: AUTHOR [+2]

Abstract

By utilizing a unique queuing technique which employs a "send" Supervisor Call (SVC) operation to allow pre-scheduling of disk read operations, I/O wait lag, and the attendant loss of throughput, is significantly improved. Standard I/O operations in paging systems of UNIX* architecture are, because of missed revolutions on disk devices, scheduling overhead and multitask competition, very slow. These factors result in a significant loss of throughput. A unique queuing technique which employs a "send" SVC operation to allow pre-scheduling of disk read operations can greatly increase throughput. This queuing technique causes the gating factor of "speed" to become the bandwidth of the data transfer hardware, rather than the software cycle.

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Input/Output Queuing for Logically Sequential I/O in a Paging System

By utilizing a unique queuing technique which employs a "send" Supervisor Call (SVC) operation to allow pre-scheduling of disk read operations, I/O wait lag, and the attendant loss of throughput, is significantly improved. Standard I/O operations in paging systems of UNIX* architecture are, because of missed revolutions on disk devices, scheduling overhead and multitask competition, very slow. These factors result in a significant loss of throughput. A unique queuing technique which employs a "send" SVC operation to allow pre-scheduling of disk read operations can greatly increase throughput. This queuing technique causes the gating factor of "speed" to become the bandwidth of the data transfer hardware, rather than the software cycle. This allows the storage device, typically disk storage, to be effectively stripped of consecutive sectors, up to the limits of memory and adapter interface speed. The gating mechanism used is a function of both the UNIX i-node structure and the physical device geometry. * Trademark of AT&T Bell Laboratories.

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