At large batch sizes virtually every expert is used, so the per-layer
routing-ids readback that mainline waits on buys nothing while forcing a
full device sync per expert tensor (3x per MoE layer). Above a batch
threshold, upload the full expert tensors through a second backend
instance on the same device (own stream) with two event-ordered staging
slots, so uploads for tensor N+1 overlap compute of tensor N.
Qwen3.6-35B-A3B pp2048 on RTX 3060 (-ncmoe 26, ub 2048): 1383 -> 1663 t/s.
Generation output verified token-identical; decode path unaffected.
Opt-in via GGML_SCHED_PREFETCH_EXPERTS=1.
Wire the existing GGML_CUDA_REGISTER_HOST path back up: after model load,
cudaHostRegister the mmap pages backing weights kept in system memory.
Recovers pageable-copy losses when MoE experts are streamed to the GPU
during prefill (n-cpu-moe): Qwen3.6-35B-A3B pp2048 1144 -> 1385 t/s on
RTX 3060. Opt-in via GGML_CUDA_REGISTER_HOST=1, unchanged otherwise.
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