Xenic: SmartNIC-accelerated distributed transacitions

https://dl.acm.org/doi/abs/10.1145/3477132.3483555

Presentation

• Distributed transactions in the datacenter

  • Our target: distributed ACID transactions are a replicated, in-memory database

  • Common approach: optimistic concurrency control + replication

  • Viability depends on efficient remote operations --> hardware acceleration

• Recent work applies RDMA

  • One-sided read/write primitives are high-performance, but restrict design

    • Impact data structure and protocol overheads

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  • Two-sided RPCs are costly

    • Add latency overhead, processing costs

  • FaRM: one-sided RDMA

  • FaSST: two-sided RPCs

  • DrTM+H: uses both

  • Ongoing debate of applying RDMA: trade-offs are necessary

• On-path SmartNICs: another option for hardware acceleration

  • Programmable remote operations, without host processing

  • Cost-effective compute: ~30% of NIC die area, 25W line-rate processing

• SmartNIC opportunities

  • Flexible CPU-bypass remote operations

  • Latency savings via stateful NIC operations, efficient PCIe DMA

  • Efficient NIC-to-NIC communication

  • But

    • Software packet pipeline --> latency overhead

    • Limited NIC resources

• Xenic

  • Distributed transactions accelerated with on-path SmartNICs

  • Key

    • Co-designed data store, spread across NIC + host DRAM

      • Minimize lookup overhead, utilizing NIC's on-board memory

    • SmartNIC function shipping

      • Offload transaction logic to avoid PCIe crossings

    • Multi-hop OCC protocols

      • Reduce communication with optimized message patterns

    • Stateful, asynchronous SmartNIC operation framework

      • Exploit the SmartNIC's hardware interfaces

• Xenic: Robinhood Data Store

  • Host DRAM contains all objects; SmartNIC caches objects and lookup hints

  • Critical path accesses: NIC memory hit or DMA read, DMA log write

    • Lookup hints limit DMA cost for cache misses

      • Cache miss: bounded DMA R

      • Cache hit: NIC DRAM

    • OCC + pinning ensure NIC/host consistency

    • 
• Xenic: SmartNIC function shipping

  • Provides SmartNIC cores as a function shipping target

  • Shipping execution can reduce overhead, depending on application-level computation and state requirements

  • Saves coordinator PCIe crossings

• Xenic: multi-hop OCC protocols

  • Ships execution to remote SmartNICs

  • Multi-hop NIC-to-NIC communication increases network efficiency

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• Evaluation

  • Robinhood + NIC lookup hints effectively reduce cost

  • SmartNIC increases DMA lookup efficiency, even for cache misses

  • For FaRM and DrTM+H, end-to-end bandwidth/latency cost

  • Better latency & throughput than RPC, RDMA, hybrid designs

  • Also measured in our paper

    • Cumulative core savings

    • Full TPC-C, Retwis, Smallbank

• Summary: high-performance, CPU-efficient distributed transactions

  • Leveraging on-path SmartNICs:

    • Avoids RDMA compromises

    • Provides a new, remote access-optimized data store

    • Selectively offloads transaction logic

    • Applies multi-hop communication patterns

    • Delivers >2x throughput over 100Gbps RDMA, latency savings relative to RPCs