Browse Prior Art Database

Analysis of Memory Hierarchies for Sequential Data Access

IP.com Disclosure Number: IPCOM000131391D
Original Publication Date: 1979-May-01
Included in the Prior Art Database: 2005-Nov-10
Document File: 11 page(s) / 43K

Publishing Venue

Software Patent Institute

Related People

Terry A. Welch: AUTHOR [+3]

Abstract

[Figure containing following caption omitted: Analytic modeling techniques permit system designers to compare memory-system alternatives quickly and easily. An example is the use of buffers -- or caches -- on disks.] Sequential data access, consisting of long sequences of accesses from consecutive logical addresses, is a major component of computer memory activity in many computer systems. An analytic study of memory hierarchy performance under sequential access, while its results will necessarily be general in nature, can nevertheless be of immediate value in evaluating design alternatives for the use of intermediatespeed memories as buffers or caches on disks. The objective of such an analysis is to provide insight into the value and type of memory-unit combinations that yield lowest cost and lowest average access times for the storage system. The strategy used in this article is to completely analyze a very simple model, contain. ing a number of possibly oversimplified assumptions, and then to quantitatively examine the effects of relaxing each assumption individually.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 9% of the total text.

Page 1 of 11

THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

This record contains textual material that is copyright ©; 1979 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Contact the IEEE Computer Society http://www.computer.org/ (714-821-8380) for copies of the complete work that was the source of this textual material and for all use beyond that as a record from the SPI Database.

Analysis of Memory Hierarchies for Sequential Data Access

Terry A. Welch

Sperry Research Center

(Image Omitted: Analytic modeling techniques permit system designers to compare memory- system alternatives quickly and easily. An example is the use of buffers -- or caches -- on disks.)

Sequential data access, consisting of long sequences of accesses from consecutive logical addresses, is a major component of computer memory activity in many computer systems. An analytic study of memory hierarchy performance under sequential access, while its results will necessarily be general in nature, can nevertheless be of immediate value in evaluating design alternatives for the use of intermediatespeed memories as buffers or caches on disks. The objective of such an analysis is to provide insight into the value and type of memory-unit combinations that yield lowest cost and lowest average access times for the storage system. The strategy used in this article is to completely analyze a very simple model, contain. ing a number of possibly oversimplified assumptions, and then to quantitatively examine the effects of relaxing each assumption individually.

The general problem of memory-hierarchy analysis concerns the proper design of various memory units having cost and access time ranges of several orders of magnitude. The objective is to select memory sizes, speeds, interconnection patterns, and datatransfer block sizes that will minimize average memory system access time for a given system cost; the strategy is to place data with the highest probability of immediate use in small, fast memory units, while holding the remainder in larger, less expensive units. This problem has received extensive study for the case of general computation involving frequent re-reference of data,l 2 3 but the study of sequential access has been more limited.4 An analytic approach for hierarchy analysis has been developed previously;5 it is applied here to the sequential- access class of problems.

Sequential access is a major component in accesses to secondary storage devices such as disks. The extension of hierarchy analysis to include secondary storage is important because of the present industry trend toward including disks in virtual memory systems with automatic data transfer procedures. Also, the availability of potential "gap- filler" technologies6 has raised interest in cache-like structures for disks. While no longer the predominant mode of secondary- storage access, sequential access is still a major storage-usage component, occurring in sc...