NanoFlow: Towards Optimal Large Language Model Serving Throughput
Authors: name: Kan Zhu, name: Yilong Zhao, name: Liangyu Zhao, name: Gefei Zuo, name: Yile Gu, name: Dedong Xie, name: Yufei Gao, name: Qinyu Xu, name: Tian Tang, name: Zihao Ye, name: Keisuke Kamahori, name: Chien-Yu Lin, name: Stephanie Wang, name: Arvind Krishnamurthy, name: Baris Kasikci

The increasing usage of Large Language Models (LLMs) has resulted in a
surging demand for planet-scale serving systems, where tens of thousands of
GPUs continuously serve hundreds of millions of users. Consequently, throughput
(under reasonable latency constraints) has emerged as a key metric that
determines serving systems' performance. To boost throughput, various methods
of inter-device parallelism (e.g., data, tensor, pipeline) have been explored.
However, existing methods do not consider overlapping the utilization of
different resources within a single device, leading to underutilization and
sub-optimal performance.
  We propose NanoFlow, a novel serving framework that exploits intra-device
parallelism, which overlaps the usage of resources including compute, memory,
and network within a single device through operation co-scheduling. To exploit
intra-device parallelism, NanoFlow introduces two key innovations: First,
NanoFlow splits requests into nano-batches at the granularity of operations,
which breaks the dependency of sequential operations in LLM inference and
enables overlapping; then, to get benefit from overlapping, NanoFlow uses an
operation-level pipeline with execution unit scheduling, which partitions the
device's functional units and simultaneously executes different operations in
each unit. NanoFlow automates the pipeline setup using a parameter search
algorithm, which enables easily porting NanoFlow to different models. We
implement NanoFlow on NVIDIA GPUs and evaluate end-to-end serving throughput on
several popular models such as LLaMA-2-70B, Mixtral 8x7B, LLaMA-3-8B, etc..
With practical workloads, NanoFlow provides 1.91x throughput boost compared to
state-of-the-art serving systems achieving 59% to 72% of optimal throughput
across ported models.