Using Dead Blocks As A Virtual Victim Cache

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Using Dead Blocks as a Virtual Victim Cache

Caches mitigate the long memory latency that limits the performance of modern processors. However, caches can be quite inefficient. On average, a cache block in a 2MB L2 cache is dead 59% of the time, i.e., it will not be referenced again before it is evicted. Increasing cache efficiency can improve performance by reducing miss rate, or alternately, improve power and energy by allowing a smaller cache with the same miss rate. This paper proposes using predicted dead blocks to hold blocks evicted from other sets. When these evicted blocks are referenced again, the access can be satisfied from the other set, avoiding a costly access to main memory. The pool of predicted dead blocks can be thought of as a virtual victim cache. A virtual victim cache in a 16-way set associative 2MB L2 cache reduces misses by 11.7%, yields an average speedup of 12.5% and improves cache efficiency by 15% on average, where cache efficiency is defined as the average time during which cache blocks contain live information. This virtual victim cache yields a lower average miss rate than a fully-associative LRU cache of the same capacity. Using an adaptive insertion policy, the virtual victim cache gives an average speedup of 17.3% over the baseline 2MB cache. The virtual victim cache significantly reduces cache misses in multi-threaded workloads. For a 2MB cache accessed simultaneously by four threads, the virtual victim cache reduces misses by 12.9% and increases cache efficiency by 16% on average Alternately, a 1.7MB virtual victim cache achieves about the same performance as a larger 2MB L2 cache, reducing the number of SRAM cells required by 16%, thus maintaining performance while reducing power and area.
Multi-Core Cache Hierarchies

Author: Rajeev Balasubramonian
language: en
Publisher: Springer Nature
Release Date: 2022-06-01
A key determinant of overall system performance and power dissipation is the cache hierarchy since access to off-chip memory consumes many more cycles and energy than on-chip accesses. In addition, multi-core processors are expected to place ever higher bandwidth demands on the memory system. All these issues make it important to avoid off-chip memory access by improving the efficiency of the on-chip cache. Future multi-core processors will have many large cache banks connected by a network and shared by many cores. Hence, many important problems must be solved: cache resources must be allocated across many cores, data must be placed in cache banks that are near the accessing core, and the most important data must be identified for retention. Finally, difficulties in scaling existing technologies require adapting to and exploiting new technology constraints. The book attempts a synthesis of recent cache research that has focused on innovations for multi-core processors. It is an excellent starting point for early-stage graduate students, researchers, and practitioners who wish to understand the landscape of recent cache research. The book is suitable as a reference for advanced computer architecture classes as well as for experienced researchers and VLSI engineers. Table of Contents: Basic Elements of Large Cache Design / Organizing Data in CMP Last Level Caches / Policies Impacting Cache Hit Rates / Interconnection Networks within Large Caches / Technology / Concluding Remarks
Emerging Technologies for Smart Cities

This book comprises the select proceedings of the International Conference on Emerging Global Trends in Engineering and Technology (EGTET 2020), held in Guwahati, India. The chapters in this book focus on the latest cleaner, greener, and efficient technologies being developed for the implementation of smart cities across the world. The broader topical sections include Smart Buildings, Infrastructures and Disaster Management; Smart Governance; Technologies for Smart Cities, and Wireless Connectivity for Smart Cities. This book will cater to students, researchers, industry professionals, and policy making bodies interested and involved in the planning and implementation of smart city projects.