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PDScope decoupled prefill from decode for MoE models on CPU-GPU nodes, lifting prefill throughput 2.5 to 10.3x and decode 2.1 to 6.1x

AspireAI community · arXiv (PPoPP'27)
When a mixture-of-experts model runs locally with limited GPU memory, most experts sit in CPU memory, and prefill and decode pull in opposite directions - prefill wants aggressive GPU loading, decode wants conservative PCIe transfers - so a phase-agnostic scheduler stalls one to serve the other. PDScope observes that expert routing is predictable in phase-specific ways and uses that to schedule and execute the two phases independently, compiling the decisions into overhead-free pipelines using a static computation graph, cache prefetching and zero-copy asynchronous I/O. On mainstream MoE models it achieved 2.5-10.3x higher prefill throughput and 2.1-6.1x higher decode throughput than existing systems, and the authors report it extends naturally to multi-batch settings. The measurements are on specific MoE models and node configurations rather than a general serving fleet.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
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