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@@ -18,7 +18,29 @@ Numbers without a measurement behind them are marked as estimates.
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  Prefill never exceeding decode by much is the tell: this deployment is not
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  compute-bound on the GPU, it is dominated by whatever runs on the host.
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- ## Bottom line: throughput is invariant, and we do not know why
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  ~3 tok/s is the ceiling for this model on 2× A40, and the reason is not the one
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  that seems obvious.
 
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  Prefill never exceeding decode by much is the tell: this deployment is not
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  compute-bound on the GPU, it is dominated by whatever runs on the host.
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+ ## The answer: host vCPU, not VRAM
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+
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+ The same configuration, on the same model, using the same two GPUs — three
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+ further GPUs sitting idle at 267 MiB — runs at **1.9× the speed** on a bigger
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+ host:
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+
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+ | Pod | GPUs | vCPU | RAM | decode |
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+ |---|---|---|---|---|
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+ | `cumv30dk07dfdy` | 2× A40 | **16** | 93 GB | 2.31 / 2.98 / 2.88 |
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+ | `okinf3ln9k8tsp` | 5× A40 | **41** | 234 GB | 4.86 / 5.28 / 5.44 / 5.64 |
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+
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+ Prefill moves even harder: 0.99 → 8.01 tok/s.
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+
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+ RunPod scales vCPU with GPU count, so renting more GPUs buys host parallelism as
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+ much as it buys VRAM. Every placement experiment below kept 70–90 GB of weights
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+ being processed by 16 saturated threads, which is why moving that work between
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+ CPU and GPU changed nothing: the CPU side was the wall in all of them.
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+
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+ This is the mechanism the section below says was missing. It was found by
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+ accident — a 5-GPU pod picked up the 2-GPU placement script before the guard
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+ was published, and ran the *identical* configuration on a larger host.
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+
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+ ## Why the placement experiments all looked the same
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  ~3 tok/s is the ceiling for this model on 2× A40, and the reason is not the one
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  that seems obvious.