Comparative study on Cache Coherence Protocols

Abstract

In this new age of technology, not only the software but also the computer architecture has been evoluted to support those softwares. The main motive of evolution of architecture day by day is to make the system faster. One of the major steps in this journey of evolution is the multi-core processor architecture. In a multi-core processor system, each core has its own cache module where they are sharing the same memory unit. For that reason, one block in one cache gets invalidate when the same block is updated into any other cache and this is called cache coherence problem. To overcome this, there are lot of research works are going on and the outcome rules or techniques are called cache coherence protocols.The main objective of this paper is to collect all those research works together and represent them in an easy way, so that we could understand their techniques to overcome the particular problem. Here it is presented a comprehensive study of those cache coherence protocols with their pros and cons. I. Introduction In the complex multilevel cache level architecture to bind the cache coherence protocol complexity we need to track the coherence information across all the levels but this leads implausible cost problem. To empower our future processors we need to embed more number of cores per chip multiprocessor. But during this we must face the off chip bandwidth wall, again to overcome this we can use a large on chip cache but because of plain large capacities of hardware the fast access could not be achieved. So commercially it is used three level cache architecture where two are used to maintain private data being closer to processor and the last one shared among cores. Have large number of cores might be helpful in some most of the cases but at the same time it is unachievable to rely on broadcast-based coherence protocols. II. Comprehensive Studies