diff --git a/serverAppConfigs-docs/LLM/LLM Performance Diagnosis.md b/serverAppConfigs-docs/LLM/LLM Performance Diagnosis.md index ca0647e..3ba2114 100644 --- a/serverAppConfigs-docs/LLM/LLM Performance Diagnosis.md +++ b/serverAppConfigs-docs/LLM/LLM Performance Diagnosis.md @@ -251,21 +251,20 @@ Knobs, in the order worth trying them (radiance GUIDE §4.5): the prefill stager's smallest pass — the startup line names it, and below it every routed layer reads its pooled experts synchronously, which costs the prefill far more than sharing saves. Counts as `engine_prefill_chunks_capped_total`. -- `--max-num-batched-tokens` — the blunt rung, and the only one older pins have. The - vendor's curve on a 48-layer MoE at 200k on two cards: chunk 512 → 1750 t/s, 1024 - → 2200, 2048 → 2706 (a 185k prompt: 138 s against 91 s), so halving the stall - costs ~19 % of prefill. Raising it past the interval buys nothing and loses expert - residency to the arena. -- `--prefill-span N` — the inverse trade: a *lone* prefill carries N intervals a step - while every shared step is planned at a smaller shared budget, which on an - expert-tiered box lends that arena back to the expert slab. Vendor TP2 - expert-tiered TTFT deltas vs a plain 2048 budget: −6.1 % at 2k, +2.3 % at 18k, - +49.1 % at 250k — long prompts only. +- `--max-num-batched-tokens` — the blunt rung, and the only one older pins have. The vendor's own + curve prices **halving the shared chunk at roughly a fifth of prefill throughput** (a 48-layer MoE + at 200k on two cards — knob pricing, not this endpoint's number, so treat it as the order of + magnitude a chunk decision costs). Raising it past the checkpoint interval buys nothing and loses + expert residency to the arena. +- `--prefill-span N` — the inverse trade: a *lone* prefill carries N intervals a step while every + shared step is planned at a smaller shared budget, which on an expert-tiered box lends that arena + back to the expert slab. The vendor's own measurement says the win is **long-prompt-only**: nothing + at short prompts, a large TTFT gain at the far end of the window. Two traps. **The arena/slab coupling makes a shared step doubly expensive on an -expert-tiered shape**: the full-plan arena takes VRAM the resident expert slab would -have had (320 MiB/card at TP2 for a 4096 budget), so the decode rows inside that step -also read experts over the link — a smaller shared budget helps twice. And **re-check +expert-tiered shape**: the full-plan arena takes VRAM the resident expert slab would have had, so the +decode rows inside that step also read experts over the link — a smaller shared budget helps twice. +And **re-check `prefix_hit_rate` / `prefix_evictions` after any chunk change**: the arena and the KV pool are the same memory, and the failure looks like turn two taking as long as turn one. @@ -276,8 +275,9 @@ Availability is a version question, not a config question: `--busy-prefill-chunk tree, and check the source clone's depth before dating a flag from `git log -S` (a `--depth 1` clone reports its own tip for every search). -Run on: [[frank-archon]] (radiance 1.0.13, TP2 `expert_tiered`, budget 2048 = interval -2048) — the measured census and the verdict for this fleet's shape are that page's. +Run on: [[frank-archon]] — the census was taken on its 3-slot radiance 1.0.13 era (budget 2048 = +interval 2048); the live 1.8.1 shape carries the two chunk knobs. The measured census and the verdict +for this fleet's shape are that page's. ## Related