针对大模型双稀疏推理设计了软硬件协同优化方案,显著提升速度。
Celty: SpMspV GPU Kernel and SIMT Co-Design for Efficient Dual-Sparse LLM Inference

- 创新使用压缩列格式,同时利用权重与激活稀疏性加速计算
- 相比cuBLAS最高提速2.8倍,双稀疏率达70%时达5.3倍
- 适合追求低延迟单用户大模型推理的系统设计者
大型语言模型(LLMs)越来越多地依赖稀疏性来降低推理开销,但以往工作多聚焦单一稀疏源——要么权重稀疏,要么激活稀疏,并针对批量多用户推理进行优化。双稀疏性(结合非结构化权重剪枝与运行时激活稀疏)在单用户解码场景下提供了模型大小、精度与延迟之间的良好权衡,但其形式为稀疏矩阵-稀疏向量(spMspV)计算,现有GPU内核处理效率低下。本文提出Celty,一种软硬件协同设计的稀疏格式、GPU内核与SIMT微架构,用于高效实现LLM推理中的spMspV。在内核层面,Celty引入运行长度压缩的压缩稀疏列(RLC-CSC)格式,支持向量化加载压缩权重列,并利用双重稀疏性跳过不必要的内存访问,共享内存用于分散部分积累。在微架构层面,Celty稀疏SIMT核心集成了流水线化的RLC解码器,消除软件层索引重构开销,并将局部寄存器文件重用于无冲突累加,直接操作相同RLC-CSC格式,无需数据布局转换。实验表明,Celty GPU内核相比cuBLAS最高提速2.8倍,相比Flash-LLM提速2.4倍;在70%双稀疏率下,搭配稀疏SIMT核心可达5.3倍加速。
原文摘要 · Abstract (English)
Large Language Models (LLMs) increasingly rely on sparsity to reduce inference cost, but most prior work targets a single sparsity source-either weight or activation-and optimizes for batched multi-user inference. Dual-sparsity, which combines unstructured weight pruning with runtime activation sparsity, offers a compelling tradeoff among model size, accuracy, and latency for single-user decoding, but formulates as a Sparse Matrix-Sparse Vector (spMspV) workload that existing GPU kernels handle poorly. We propose Celty, a co-designed sparse format, GPU kernel, and SIMT microarchitecture for efficient spMspV in LLM inference. At the kernel level, Celty introduces a Run-Length Compressed CSC (RLC-CSC) format that enables vectorized loading of compressed weight columns and exploits both sparsity sources to skip unnecessary memory accesses, with shared memory used for scattered partial-product accumulation. At the microarchitecture level, the Celty Sparse SIMT Core integrates a pipelined RLC decoder to eliminate software-level index reconstruction and repurposes local register files for conflict-free accumulation-operating directly on the same RLC-CSC format without data layout changes. The Celty GPU kernel achieves up to 2.8x speedup over cuBLAS and 2.4x over Flash-LLM. With the Sparse SIMT Core, speedups reach up to 5.3x over cuBLAS at 70% dual-sparsity.
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