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Memory Usage Estimator

IP.com Disclosure Number: IPCOM000079377D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 20K

Publishing Venue

IBM

Related People

Kelly, WW: AUTHOR

Abstract

A memory in a data-processing system can be monitored to periodically record whether an access has been made to a particular page of the memory, and whether any such access is a store operation which changes the data content of the location. The result of this monitoring is a record of the memory activity for each of a succession of time intervals. This record can be converted to an estimate of memory usage, according to the equations listed below.

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Memory Usage Estimator

A memory in a data-processing system can be monitored to periodically record whether an access has been made to a particular page of the memory, and whether any such access is a store operation which changes the data content of the location. The result of this monitoring is a record of the memory activity for each of a succession of time intervals. This record can be converted to an estimate of memory usage, according to the equations listed below.

In a hierarchical memory system, data held on a large-capacity memory device such as a magnetic disk is organized as pages, and pages that are to be operated on by the system are brought into a smaller memory. If the main memory is too small for its intended operation, much of the memory operating time is spent unproductively swapping pages between the large memory and the small memory. Thus, memory usage information helps the memory user to select a memory of appropriate size for his data processing operations.

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There are N pages in the memory that is being monitored. For the paging algorithm that recently unused pages are removed before recently used pages are removed, an unused page has a progressively higher likelihood of being removed with each successive monitoring interval. A decay factor, D, equals the estimated number of intervals that a page will remain in memory if it is unused.

In processing the information produced by the monitoring operation, each page is given a counter number, Ei, that equals the number of following intervals that the page may remain in memory without use before it may be removed. When a page is brought into memory and whenever it is accessed, its value of Ei is set to t...