Packet Processing Architecture Using Last-Level-Cache Slices and Interleaved 3D-Stacked DRAM

Abstract

Packet processing performance of Network Function Virtualization (NFV)-aware environment depends on the memory access performance of commercial-off-the-shelf (COTS) hardware systems. Table lookup is a typical example of packet processing, which has a significant dependence on memory access performance. Thus, the on-chip cache memories of the CPU are becoming more and more critical for many high-performance software routers or switches. Moreover, in the carrier network, multiple applications run on top of the same hardware system in parallel, which requires the capacity of cache memories. In this paper, we propose a packet processing architecture that enhances memory access parallelism by combining on-chip last-level-cache (LLC) slices and off-chip interleaved 3 Dimensional (3D)-stacked Dynamic Random Access Memory (DRAM) devices. Table entries are stored in the off-chip 3D-stacked DRAM, so that memory requests are processed in parallel by using bank interleaving and channel parallelism. Also, cached entries are distributed to on-chip LLC slices according to a memory address-based hash function so that each CPU core can access on-chip LLC in parallel. The evaluation results show that the proposed architecture reduces the memory access latency by 62 % and 12 % and increases the throughput by 108 % and 2 % with reducing blocking probability of memory requests 96 % and 50 %, compared to the architecture with on-chip shared LLC and that without on-chip LLC, respectively.