A proposal for a new hardware cache monitoring architecture

The analysis of the memory access behavior of applications, an essential step for a successful cache optimization, is a complex task. It needs to be supported with appropriate tools and monitoring facilities. Currently, however, users can only rely on either simulation based approaches, which deliver a large degree of detail but are restricted in their applicability, or on hardware counters embedded into processors, which allow to keep track of very few, mostly global events and hence only provide limited data. In this work a proposal for novel hardware monitoring facility is presented which exhibits both the details of traditional simulations and the low-overhead of hardware counters. Like the latter approach, it is also targeted towards an implementation within the processor for a direct and nonintrusive access to caches and memory busses. Unlike traditional counters, however, it delivers a detailed picture of the complete memory access behavior of applications. This is achieved by generating so-called memory access histograms, which show access frequencies in relation to the applications address space. Such spatial memory access information can then be used for efficient program optimization by focusing on the code and data segments which were found to exhibit a poor cache behavior.