A General, Tractable and Accurate Model for a Cascade of Caches

Abstract: Performance evaluation of caching systems is an old and widely investigated research topic. The research community is once again actively working on this topic because the Internet is evolving towards new transfer modes, which envisage to cache both contents and instructions within the network. In particular, there is interest in characterizing multi-cache systems, in which requests not satisfied by a cache are forwarded to other caches. In this field, this paper contributes as follows. First, we devise a simple but accurate approximate analysis for caches fed by general "renewal" traffic patterns. Second, we characterize and model the traffic statistics for the output (miss) stream. Third, we show in the simple example case of tandem caches how the resulting output stream model can be conveniently exploited to analyze the performance of subsequent cache stages. The main novelty of our work stems in the ability to handle traffic patterns beyond the traditional independent reference model, thus permitting simple assessment of cascade of caches as well as improved understanding of the phenomena involved in cache hierarchies.