Browse Prior Art Database

Exclusive Use Directory and Inode Caching

IP.com Disclosure Number: IPCOM000037327D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Emma, PG: AUTHOR [+5]

Abstract

A method of selectively caching the file system information of a particular operating system for the purpose of improving performance in large time-sharing contexts is described. It should be applicable to large System 370 configurations.

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Exclusive Use Directory and Inode Caching

A method of selectively caching the file system information of a particular operating system for the purpose of improving performance in large time-sharing contexts is described. It should be applicable to large System 370 configurations.

IBM's VM/CMS operating system has a performance advantage in large time- sharing configurations over traditional UNIX* implementations. CMS keeps file system information in the private storage of each virtual machine, at least for many mini-disks. In UNIX this same information is logically kept not in memory but on secondary storage. Most UNIX implementations "cache" blocks of information from DASD in main memory, but this information is in "system" storage, not user storage. As a consequence, any UNIX utilities which access this file system information must coordinate such access with the operating system using a system call.

In the present invention, information about some files that are likely to be used exclusively by one user in almost all cases is cached in main memory or virtual memory. In traditional UNIX implementations, this is the directory entry and corresponding inode contents for the selected files. The globally accessible copies of this information are marked inaccessible and programs would be free to read and write the information without coordination with other users or system tasks. In traditional UNIX implementations, this information is "hidden" from individual processes in system space, and this "hiding" is usually deemed beneficial (aside from its poss...