Octans: Optimal Placement of Service Function Chains in Many-Core Systems

Network Function Virtualization (NFV) has the potential to offer service delivery flexibility and reduce overall costs by running service function chains (SFCs) on commodity servers with many cores. Existing solutions for placing SFCs in one server treat all CPU cores as equal and allocate isolated CPU cores to different network functions (NFs). However, advanced servers often adopt Non-Uniform Memory Access (NUMA) architecture to improve the scalability of many-core systems. CPU cores are grouped into nodes, incurring performance bottleneck due to cross-node memory access and intra-node resource contention. Our evaluation shows that randomly selecting cores to place NFs in an SFC could suffer from 39.2% lower throughput comparing to an optimal placement solution. In this paper, we propose Octans, an NFV orchestrator to achieve maximum aggregate throughput of all SFCs in many-core systems. Octans first formulates the optimization problem as a Non-Linear Integer Programming (NLIP) model. Then we identify the key factor for problem solving as evaluating the throughput drop of an NF caused by other NFs in the same SFC or different SFCs, i.e. performance drop index, and propose a formal and precise prediction model based on system level performance metrics. Finally, we propose an efficient heuristic algorithm to quickly find near-optimal placement solutions. We have implemented a prototype of Octans. Extensive evaluation shows that Octans significantly improves the aggregate throughput comparing to two state-of the-art placement mechanisms by 26.7%$\sim$51.8%, with very low prediction errors of SFC performance (an average deviation of 2.6%). Moreover, Octans could quickly find a near-optimal placement solution with tiny optimality gap (1.2%$\sim$3.5%).