inference-tradeoffs-explained

Case study

Offline batch

SLOs: time to first token at most 60,000 ms and time per output token at most 500.0 ms, met by at least 90% of requests at capacity. The workload, as the sweep generates it:

Bulk summarisation or labelling: nobody is waiting, so the SLOs are loose (60 s, 0.5 s a token) and throughput and cost per token decide (our choice).

The frontier

Goodput per GPU against cost per million tokens, starting on this workload (play to compare the others; pick other metrics below).

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Levers that change sign

Levers whose effect on goodput per GPU (H100) points one way here and the other way on at least one other workload: + more goodput than the baseline, − less, 0 within ±2%.

LeverOffline batchChatCoding agentLong-context RAGReal-time voice
Chunked prefill, 512-token budget−+−++
Chunked prefill, 2,048-token budget++−++
Disaggregated 1P1D (TP4 each)−−−−+
Disaggregated 1P1D, paged decode, prefix-cached prefill−++++
1 x TP8−−+−−
FP8 KV cache+++0−

Other case studies: Chat · Coding agent · Long-context RAG · Real-time voice.