多台Intel AI PC协同运行大模型,实现高效分布式推理。
Pre-Compiled Pipeline Shards for Distributed LLM Inference on Intel AI PC Fleets
- 将大模型按层切分并预编译为OpenVINO图,在多设备上流水线执行。
- 通过优化激活传递和请求交错,两节点部署实现1.79倍于单机的吞吐量。
- 适合在边缘设备集群上部署超大规模语言模型,支持交互式响应。
现代Intel AI PC配备集成GPU和NPU,拥有16GB以上统一内存,但常处于空闲状态。单一设备无法容纳如70B参数大模型。本文展示,若干AIPC通过普通网络协作,可服务超出单机能力的模型。采用流水线并行:模型按层切分为各阶段的碎片,每个碎片预编译为OpenVINO图,每台机器运行一个碎片并传递激活值。三项技术使系统足够高效:第一,通过注入beam_idx Gather触发OpenVINO GPU优化(IndirectKVCache融合),恢复未切分模型的速度;第二,利用状态化OpenVINO模型的推测解码;第三,通过跨阶段交错多个用户请求并携带独立缓存(微批处理),实现并发服务。两个节点部署的Llama 3.1 8B INT4模型可同时服务两名用户,吞吐量达单用户时的1.79倍,且在模拟广域延迟下优势更明显。该设计可扩展至70B模型:四个Lunar Lake AI PC在Intel Tiber Cloud上部署,单用户实现交互式速度,输出与无推测解码的同配置流水线完全一致。代码、原始基准日志与复现脚本已开源。
原文摘要 · Abstract (English)
Modern Intel AI PCs ship capable integrated GPUs and NPUs with 16+ GB of unified memory, and they spend considerable time idle. That is not enough memory to fit a large model such as a 70B-parameter LLM. We show that a handful of AIPCs, working together over an ordinary network, can serve models beyond the capability of any single one. We use pipeline parallelism: a model is split by layer into per-stage shards, each pre-compiled into an OpenVINO graph, so that every machine runs one shard and passes activations to the next. Three techniques make this fast enough to be useful. First, we recover the speed of the unsplit model: a naive per-stage export runs well below monolithic inference because it misses an OpenVINO GPU optimization, and injecting a beam_idx Gather into each shard triggers that optimization (the IndirectKVCache fusion) and brings the shards to parity. Second, we leverage speculative decoding on stateful OpenVINO models. Third, the pipeline serves several users at once by interleaving their requests across the stages, each request carrying its own cache (micro-batching). Together, a two-node Llama 3.1 8B INT4 pipeline serves two concurrent users at 1.79x the single-user throughput of the unsplit model on the same hardware, and the gap widens under simulated wide-area latency. The same design scales to a 70B model that no single fleet member can hold: a four-node deployment of Lunar Lake AI PCs on Intel Tiber Cloud serves a single user at interactive speed, with output token-for-token identical to the same four-node pipeline decoding without speculation. Code, raw benchmark logs, and reproduction scripts ship as a self-contained package at https://github.com/labscommunity/pipeline-sharded-inference-paper (in the top-level reproduction/ directory).
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