通过感知硬件差异优化专家分配,显著减少大模型推理中的慢节点问题。
ViBE: Co-Optimizing Workload Skew and Hardware Variability for MoE Serving

- 根据GPU实际性能动态分配专家,让快设备处理高负载任务
- 在真实场景下使延迟不均衡降低,服务达标率提升14%
- 适用于大规模部署的LLM服务,尤其对硬件异构敏感的场景
在分布式混合专家(MoE)推理中,输入相关的令牌路由与GPU性能差异共同导致同步执行下的持续慢节点问题,最慢的GPU决定层延迟。现代加速器固有的性能波动源于制造差异、功耗限制和热条件,造成名义相同的GPU间存在可测量的执行时间差异。核心挑战在于MoE执行时间不平衡来自工作负载偏斜与硬件异质性的交互作用:令牌路由产生不均且随层变化的专家负载,而GPU吞吐量取决于设备特性和工作负载强度。先前方法缓解路由偏斜但假设硬件同质,仅优化令牌平衡而非执行延迟,导致即使令牌分配均衡,仍存在硬件引发的慢节点。为此,我们提出变异性感知的专家分箱(ViBE),一种硬件感知的专家放置框架,以最小化跨GPU的执行时间不平衡。ViBE结合每个GPU的性能建模与专家激活分析,将高负载专家分配给更快设备,低负载专家分配给较慢设备,从而在不改变模型语义或硬件的前提下减少层级慢节点。由于工作负载特征和有效GPU吞吐量可能随服务条件变化,ViBE支持轻量级再校准,可在性能漂移时刷新路由与性能估计。结果表明,ViBE持续降低执行时间不平衡,提升服务等级目标(SLO)达成率14%,同时将P90首字节时间(TTFT)降低最多45%。我们进一步发现,硬件变异性的影响随规模增大而加剧,凸显了在高效高利用率大模型服务中考虑变异性的重要性。
原文摘要 · Abstract (English)
In distributed Mixture-of-Experts (MoE) inference, input-dependent token routing interacts with GPU performance variability to create persistent stragglers under synchronized execution, where the slowest GPU determines layer latency. This performance variability is inherent to modern accelerators: manufacturing variation, power limits, and thermal conditions introduce measurable execution-time differences across nominally identical GPUs. The core challenge is that MoE execution-time imbalance arises from the interaction of workload skew and hardware asymmetry. Token routing produces uneven and layer-varying expert loads, while GPU throughput depends on device-specific operating characteristics and workload intensity. Prior work mitigates routing skew but assumes homogeneous hardware, optimizing token balance rather than execution latency. As a result, even balanced token assignments can leave hardware-induced stragglers unaddressed. Thus, we propose Variability-Informed Binning of Experts (ViBE), a hardware-aware expert placement framework that minimizes execution-time imbalance across GPUs. ViBE combines per-GPU performance modeling with expert activation profiling to assign high-load experts to faster devices and low-load experts to slower ones, reducing layer-level stragglers without modifying model semantics or hardware. Because both workload characteristics and effective GPU throughput can shift across serving conditions, ViBE supports lightweight recalibration under workload/performance drift to refresh its routing and performance estimates when needed. Results show that ViBE consistently reduces execution-time imbalance and improves SLO attainment by 14%, while lowering P90 TTFT by up to 45%. We further show that the impact of hardware variability increases at scale, making variability-aware placement important for efficient, high-utilization LLM serving.
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