RingLeader: Efficiently Offloading Intra-Server Orchestration to NICs.

Careful orchestration of requests at a datacenter server is crucial to meet tight tail latency requirements and ensure high throughput and optimal CPU utilization. Orchestration is multi-pronged and involves load balancing and scheduling requests belonging to different services across CPU resources, and adapting CPU allocation to request bursts. Centralized intra-server orchestration offers ideal load balancing performance, scheduling precision, and burst-tolerant CPU re-allocation. However, existing software-only approaches fail to achieve ideal orchestration because they have limited scalability and waste CPU resources. We argue for a new approach that offloads intra-server orchestration entirely to the NIC. We present RingLeader, a new programmable NIC with novel hardware units for software-informed request load balancing and programmable scheduling and a new light-weight OS-NIC interface that enables close NIC-CPU coordination and supports NIC-assisted CPU scheduling. Detailed experiments with a 100 Gbps FPGA-based prototype show that we obtain better scalability, efficiency, latency, and throughput than state-of- the-art software-only orchestrators including Shinjuku and Caladan.