FIFO anomaly is unbounded

Virtual memory of computers is usually implemented by demand paging. For some page replacement algorithms the number of page faults may increase as the number of page frames increases. Belady, Nelson and Shedler constructed reference strings for which page replacement algorithm FIFO produces near twice more page faults in a larger memory than in a smaller one. They formulated the conjecture that 2 is a general bound. We prove that this ratio can be arbitrarily large

Near-optimal replacement policies for shared caches in multicore processors

An optimal replacement policy that minimizes the miss rate in a private cache was proposed several decades ago. It requires knowing the future access sequence the cache will receive. There is no equivalent for shared caches because replacement decisions alter this future sequence. We present a novel near-optimal policy for minimizing the miss rate in a shared cache that approaches the optimal execution iteratively. During each iteration, the future access sequence is reconstructed on every miss interleaving the future per-core sequences, taken from the previous iteration. This single sequence feeds a classical private-cache optimum replacement policy. Our evaluation on a shared last-level cache shows that our proposal iteratively converges to a near-optimal miss rate that is independent of the initial conditions, within a margin of 0.1%. The best state-of-the-art online policies achieve around 65% of the miss rate reduction obtained by our near-optimal proposal. In a shared cache, miss rate optimization does not imply the optimization of other metrics. Therefore, we also propose a new near-optimal policy to maximize fairness between cores. The best state-of-the-art online policy achieves 60% of the improvement in fairness seen with our near-optimal policy. Our proposals are useful both for setting upper performance bounds and inspiring implementable mechanisms for shared caches.The authors acknowledge support from grants (1) PID2019-105660RB-C21 and PID2019-107255GB-C22 from Agencia Estatal de Investigación (AEI) from Spain and European Regional Development Fund (ERDF); (2) gaZ: T58_20R research group from Aragón Government and European Social Fund (ESF); and (3) 2014-2020 "Construyendo Europa desde Aragón" from European Regional Development Fund (ERDF).Peer ReviewedPostprint (author's final draft

NASA Tech Briefs Index, 1978

Approximately 601 announcements of new technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Emphasis is placed on information considered likely to be transferrable across industrial, regional, or disciplinary lines. Subject matter covered includes: electronic components and circuits; electron systems; physical sciences; materials; life sciences; mechanics; machinery; fabrication technology; and mathematics and information sciences

NASA Tech Briefs Index 1978

Tech Briefs are short announcements of new technology derived from the research and development activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This Index to NASA Tech Briefs contains abstracts and four indexes -- subject, personal author, originating Center, and Tech Brief number -- for 1978 Tech Briefs

An Introduction to Database Systems

This textbook introduces the basic concepts of database systems. These concepts are presented through numerous examples in modeling and design. The material in this book is geared to an introductory course in database systems offered at the junior or senior level of Computer Science. It could also be used in a first year graduate course in database systems, focusing on a selection of the advanced topics in the latter chapters

Data bases and data base systems related to NASA's aerospace program. A bibliography with indexes

This bibliography lists 1778 reports, articles, and other documents introduced into the NASA scientific and technical information system, 1975 through 1980