* [Perf][SM70] 4096-token prefill chunks: native Q4096 79T attention and reserved long-prefix workspaces
The 79T Q8000/Q8192 prefill attention needs budgets of 8000+, so 4096-token
chunks fell back to Split-D at ~47 TFLOPS for long prefixes (250K TTFT +22%).
Add a native Q4096 specialization of the same FP32-accumulated architecture
(256-token tail, own namespace, workspace slots and a half-height score
buffer), dispatched for Q4000..Q4096 once KV reaches 8192 keys; Q4000..Q4095
are leading-padded. Operator medians at KV128K/248K are ~62 TFLOPS.
Reserve the E4M3 prefix bridge (for max_model_len) and the bridge tail
during memory profiling instead of growing them by doubling at the first
long prompt, which ran a 128K request out of memory at 4096-token chunks.
The Qwen3.8-27B NVFP4 + DFlash2 release profile now uses 4096-token chunks
and 0.86 memory utilization and supports V100-SXM2 16GB: 4.07 GiB of KV per
GPU against 3.33 GiB for 8192/0.92, TTFT within 1% to 32K and +3.9% at 250K,
decode and speed-fixture rounds unchanged, 250K + four concurrent 64K
requests without OOM.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* [Style] Format the 79T owner dispatch and type the Q8000 prefill reason
clang-format reflows PrefillOwner::run; mypy needs the optional reason
declared before its branches.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
