Mixture-of-Experts Inference Optimization Study
Launch-Bound and Substitutable: Why Three Inference Optimizations Fail to Pay Off in Mixture-of-Experts Models
The findings impact MoE deployment efficiency for researchers and companies using these models in production environments.
The paper examines three inference optimizations on OLMoE-1B-7B, DeepSeek-V2-Lite, and Qwen3-30B-A3B models. Fused Triton kernels show 5.6x to 9.0x improvement in isolation but only 0.999x end-to-end against a 1.07x ceiling. INT4 quantization changes 0.53 of eight experts per token, yet reproduces only 2.7% of quality loss, indicating substitutability. Removing 23 torch.compile graph breaks makes the model three times slower.
Launch-Bound and Substitutable: Why Three Inference Optimizations Fail to Pay Off in Mixture-of-Experts Models
Mixture-of-Experts (MoE) models route each token to a few of many expert networks, and that routing is data- dependent in a way standard inference optimizations do not ex- pect. This paper measures what three of them actually deliver on OLMoE-1B-7B, DeepSeek-V2-Lite, and Qwen3-30B-A3B. Fused Triton kernels reach 5.6x to 9.0x in isolation but 0.999x end to end against a measured 1.07x ceiling, because the model spends its time waiting on roughly a thousand kernel launches per forward pass rather than on the arithmetic those kernels improve. INT4 quantization changes on average 0.53 of the eight selected experts per token position, yet replaying exactly those changed routes through full-precision weights reproduces only 2.7% of the quality loss, which makes the experts substitutable rather than specialized. Removing all 23 torch.compile graph breaks, the step prior work treats as the structural fix, makes the model three times slower. A fourth result ties the three together: leaving the routers in FP16 lowers drift by 20% while raising loss, so routing fidelity and output quality are separable objectives. Every number recomputes from committed per-token route dumps.