Self-described buffer: A novel mechanism to improve packet I/O efficiency in Linux

Socket buffer (SKB) is the standard data structure for exchanging packets and their control information between NIC driver and protocol stack. The overhead of dynamic SKB management has been considered as the significant bottleneck in packet I/O. Some novel non-SKB mechanisms, such as DPDK, were thus proposed to solve the problem. However, these mechanisms usually cannot be widely adopted in the data path of most packet forwarding applications, due to their incompatibility with SKB. In this paper, a new SKB-compatible mechanism, namely Self-described buffer (SDB), is proposed to improve the efficiency of packet I/O. SDB eliminates SKB allocation/deallocation overhead by offloading SKB management into NIC hardware. It also reduces the overhead of dynamic binding/unbinding operations existed in SKB management by statically binding related information in advance using the free space of Databuf. To evaluate the proposed approach, a SDB-enabled NIC and its driver has been designed and implemented based on FPGA. Experimental results show that the proposed SDB achieves 2× throughput compared with a traditional SKB mechanism in raw packet forwarding, and 34.75% improvement for typical network forwarding applications (e.g. IP forwarding, Bridge forwarding and SDN forwarding) on average.