A typical SmartNIC (SNIC) integrates a processor comprising Arm CPU and accelerators with a conventional NIC. The processor is designed to energy-efficiently execute network functions frequently used by datacenter applications. With such a processor, the SNIC has promised to notably improve the system-wide energy efficiency of datacenter servers. Nevertheless, the latest trend of integrating accelerators into server CPUs for these functions sparks a question on the SNIC processor’s superiority over a host processor (i.e., server CPU with accelerators) in system-wide energy efficiency, especially under given tail latency constraints. Answering this question, we first take an Intel Xeon processor, integrated with various accelerators (e.g., QuickAssist Technology), as a host processor, and then compare it to an NVIDIA BlueField-2 SNIC processor. This uncovers that (1) the host accelerator, coupled with a more powerful memory subsystem, can outperform the SNIC accelerator, and (2) the SNIC processor can improve system-wide energy efficiency only at low packet rates for most functions under tail latency constraints. To provide high system-wide energy efficiency without compromising tail latency at any packet rates, we propose HAL, consisting of a hardware-based load balancer and an intelligent load balancing policy implemented inside the SNIC. When HAL determines that the SNIC processor cannot efficiently process a given function beyond a specific packet rate, it limits the rate of packets to the SNIC processor and lets the host processor handle the excess. We implement a HAL-enabled SNIC with a commodity FPGA and a BlueField-2 SNIC, plug it into a commodity server, and run 10 popular network functions. Our evaluation shows that HAL can improve the system-wide energy efficiency and throughput of the server running these functions by 31% and 10%, respectively, without notably increasing the tail latency.

Intra-host networks, including heterogeneous devices and interconnect fabrics, have become increasingly complex and crucial. However, intra-host networks today do not provide sufficient manageability. This prevents data center operators from running a reliable and efficient end-to-end network, especially for multi-tenant clouds. In this paper, we analyze the main manageability deficiencies of intra-host networks and argue that a systematic solution should be implemented to bridge this function gap. We propose two key building blocks for a manageable intra-host network: a fine-grained monitoring system and a holistic resource manager. We discuss the research questions associated with realizing these two building blocks.