Reliability improvement in private non-uniform cache architecture using two enhanced structures for coherence protocols and replacement policies

Abstract

In this paper, a comprehensive study is first conducted to investigate the effects of cache coherence protocols and cache replacement policies on the characteristics of NUCA in current many-core processors. The main focus of this study is to analyze the effects of coherence protocols and replacement policies on the vulnerability of caches. The outcomes of this analysis indicate two facts: (i) Differences in handling write operations play an important role to make distinction in favor of or against a cache coherence protocol; (ii) Near-optimal solutions for replacement problem, aimed at enhancing the performance, can also make positive influence on reduction of cache vulnerability factor. Based on the results of first step, two schemes are introduced to enhance the reliability of caches by applying some modification on the structures of cache coherence protocols and cache replacement policies. The first scheme tries to manage sharing of the dirty data items among different same-level caches. The second helps to give priority and more opportunity to old dirty blocks than clean blocks for replacement. The proposed schemes reveal about 18% improvement in MTTF, with negligible performance, bandwidth and energy consumption overhead compared to previous cache structures.