Page Classifier and Placer: A Scheme of Managing Hybrid Caches

Hybrid cache architecture (HCA), which uses two or more cache hierarchy designs in a processor, may outperform traditional cache architectures because no single memory technology can deliver the optimal power, performance and density at the same time. The general HCA scheme has also been proposed to manage cache regions that have different usage patterns. However previous HCA management schemes control data placement at cache set level and are oblivious to software’s different power and performance characteristics in different hardware cache regions. This hardware-only approach may lead to performance loss and may fail to guarantee quality of service. We propose a new HCA approach that enables OS to be aware of underlying hybrid cache architecture and to control data placement, at OS page level, onto difference cache regions. Our approach employs a light-weighted hardware profiler to monitor cache behaviors at OS page level and to capture the hot pages. With this knowledge, OS will be able to dynamically select different cache placement policies to optimize placement of data to achieve higher performance, lower power consumption and better quality of service. Our simulation experiments demonstrate that the proposed hybrid HCA achieves 7.8% performance improvement on a dual-core system compared to a traditional SRAM-only cache architecture and at the same time reduces area cost.