KTransformers: Unleashing the Full Potential of CPU/GPU Hybrid Inference for MoE Models

Abstract

Due to the sparse nature of Mixture-of-Experts (MoE) models, they are particularly suitable for hybrid CPU/GPU inference, especially in low-concurrency scenarios. This hybrid approach leverages both the large, cost-effective memory capacity of CPU/DRAM and the high bandwidth of GPU/VRAM. However, existing hybrid solutions remain bottlenecked by CPU computation limits and CPU-GPU synchronization overheads, severely restricting their ability to efficiently run state-of-the-art large MoE models, such as the 671B DeepSeek-V3/R1.This paper presents KTransformers, a high-performance inference system designed specifically for efficient heterogeneous computing of diverse MoE models. KTransformers employs optimized, AMX-specialized kernels that fully utilize the computational capabilities of modern CPUs and incorporates an asynchronous CPU-GPU task scheduling mechanism to minimize overhead - achieving 4.62-19.74× prefilling speedups and 1.25-4.09× decoding speedups compared to existing systems.Furthermore, we propose a novel Expert Deferral mechanism that strategically enhances the potential for overlapping CPU and GPU computations, increasing CPU utilization from typically below 75% to almost 100%. This yields up to 1.45× additional throughput beyond the aforementioned optimizations, with an average model accuracy drop of no more than 0.5% across a diverse set of benchmarks.The resulting system, KTransformers, substantially enhances the accessibility of large MoE models for local users who prioritize security or intend to dig into the internals of the models. As a result, it has already been widely adopted within both the open-source community and industry.