Operator-directed: raise context to the model's native maximum and take as much KV
as the card safely allows, and expose the seat through LiteLLM as `gen-large`.
max_model_len 131,072 -> 262,144
KV cache 8.76 -> 14.00 GiB (332,721 -> 560,654 tokens)
concurrency 2.54x@128K -> 2.14x@262K
⚠ 16.00 GiB WAS TRIED FIRST AND IS TOO AGGRESSIVE. A 155,497-token non-repeating
prefill drove GPU 2 to 97,074 of 97,887 MiB and the caching allocator logged "OOM on
device 0 while trying to allocate 488636416 bytes (free: 422117376)" -- 466 MiB wanted
against 403 MiB free. The request completed, so nothing failed visibly; that is one
step before the shape that crashed stacks/mog-sec twice on 2026-09-10 (~1.04 GiB
wanted, ~600 MB free). Backed off to 14.00 GiB, which re-probes clean: zero allocator
warnings, a 155,557-token prefill in 14.2 s, and 2,085 MiB still free at peak.
The reason the first estimate was wrong is worth keeping, because it is not obvious
and it inverts the usual advice: --kv-cache-memory makes vLLM SKIP MEMORY PROFILING
ENTIRELY and ignore --gpu-memory-utilization. The profiler was the thing accounting
for deep-prefill activation, so pinning bytes switched off the protection that the
pin was supposed to formalise. vLLM's own "--kv-cache-memory=18745235968 (17.46 GiB)
to fully utilize gpu memory" line is computed from a profile measured at
max-num-batched-tokens depth and sits 3.5 GiB above what a 150K-token request
survives; open #54764 compounds it, since PLE short-conv prefill pads every request
in a batch to the batch-MAX query length.
max-num-batched-tokens stays at 8192 -- it is what bounds the activation peak, and
doubling max_model_len left the profiled peak unchanged at 1.65 GiB precisely because
the peak tracks chunk size, not context length.
Gateway: `gen-large` added to the LiteLLM model_list, pointing at fv-ml1:8022. One
alias on purpose -- a single alias cannot trip the shared-config enable_thinking
mutation footgun, which needs two over the same (model, api_base). Sampling is the
checkpoint's own declared set (temp 1.0 / top_p 0.95 / top_k 20); presence_penalty,
min_p and repetition_penalty are left unset because the checkpoint declares no
canonical value for them. Verified registered for both the infra-ops admin key and
the shared all-agents key, since a new model behind a scoped allowlist 403s silently.
Also adds services/flash-next-mtp-bench/ -- the MTP measurement campaign and its
rationale. MTP stays off, but on "not yet measured here" rather than on vLLM's
4xH100 recipe number, which is a cross-harness comparison and not evidence about a
TP=1 Blackwell seat.
vh
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