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.
 
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