[docs] Retune the Qwen3.8-27B RTX 5090 DFLASH2 cells against 1cf2b8c (#35786)

2026-08-20 21:54:51 -07:00
parent 78c964d9d7
commit 3efa057449
2 changed files with 71 additions and 37 deletions
@@ -22,7 +22,11 @@ pip install uv
 uv pip install sglang

 # For the DFLASH2 cells only — DFlash2 selector support is newer than the
-# latest release, so install from source (Method 2) instead of the line above.
+# latest release, so build from the commit those cells were validated on
+# instead of the line above:
+# git clone https://github.com/sgl-project/sglang.git && cd sglang
+# git checkout 1cf2b8c54d81802abc15dcf23a29b9cc687bc01e   # PR #35496
+# uv pip install -e "python[all]"
 ```

 Then run the **Python** output of the command panel below in that environment.
@@ -34,9 +38,11 @@ Then run the **Python** output of the command panel below in that environment.
 ```bash Command
 docker pull lmsysorg/sglang:qwen38-27b

-# For the DFLASH2 cells only — that tag predates DFlash2 selector support,
-# so pull a nightly built from main instead:
-# docker pull lmsysorg/sglang:dev
+# For the DFLASH2 cells only — that tag predates DFlash2 selector support.
+# Build the image from the commit those cells were validated on instead:
+# git clone https://github.com/sgl-project/sglang.git && cd sglang
+# git checkout 1cf2b8c54d81802abc15dcf23a29b9cc687bc01e   # PR #35496
+# docker build -t sglang:dflash2 -f docker/Dockerfile .
 ```

 For how to launch the image, see [Install → Method 3: Using Docker](../../../docs/get-started/install#method-3-using-docker). Substitute the inner `sglang serve ...` with what the command generator below produces.
@@ -46,14 +52,16 @@ For how to launch the image, see [Install → Method 3: Using Docker](../../../d
 </Tabs>

 <Warning>
-**DFLASH2 needs a build that tracks main.** DFlash2 landed in
-[#35371](https://github.com/sgl-project/sglang/pull/35371), and DFlash2 + NVFP4
-— the quantized `lm_head` path — in
-[#35496](https://github.com/sgl-project/sglang/pull/35496). Both are newer than
-the pinned `lmsysorg/sglang:qwen38-27b` tag and than the latest PyPI release; a
-build without #35496 fails on the NVFP4 cells at boot with `requires a dense
-FP16/BF16/FP32 target lm_head`. Every other recipe on this page — no
-speculation, MTP, DSpark — runs on the pinned tag as written.
+**DFLASH2 needs a build from `1cf2b8c` (PR
+[#35496](https://github.com/sgl-project/sglang/pull/35496)) or newer.** DFlash2
+landed in [#35371](https://github.com/sgl-project/sglang/pull/35371) and its
+quantized-`lm_head` path — what the NVFP4 cells need — in #35496, both newer
+than the pinned `lmsysorg/sglang:qwen38-27b` tag and than the latest PyPI
+release. A build without #35496 fails on the NVFP4 cells at boot with `requires
+a dense FP16/BF16/FP32 target lm_head`. The DFLASH2 pins on this page were
+measured on `1cf2b8c` exactly, which is why both install paths above check that
+commit out rather than tracking a moving branch. Every other recipe on this
+page — no speculation, MTP, DSpark — runs on the pinned tag as written.
 </Warning>

 </Accordion>
@@ -269,18 +277,18 @@ checkpoint's calibration scales automatically.
  RTX PRO 6000 BF16/FP8 cells boot and serve; on H200, DGX Spark and GB300
  those cells carry the **Final Verification In Progress**
  badge. The
-  RTX PRO 6000 recipe needs no changes. On the 32GB RTX 5090 prefer
-  `--mamba-ssm-dtype bfloat16` at `--mem-fraction-static 0.90`: measured
-  strictly better than float32 for this draft (6.1 vs 8.3 ms TPOT, accept
-  3.30 vs 3.09) — the opposite of the EAGLE trade, so measure before assuming.
-  float32 still fits, but only at `--mem-fraction-static 0.945` with
-  `--mamba-full-memory-ratio 10` pinned in place of the balanced value: the
-  L = 9216 ratio leaves the fp32 state pool one slot short at every
-  serviceable mem-fraction (0.94 allocates four of Low-Latency's five slots;
-  0.95 OOMs at runtime), and the re-weighted split leaves the Low-Latency KV
-  pool a single-request envelope (~9.4k tokens) — no headroom for longer
-  requests or radix reuse. The panel's DFLASH2 option applies these re-pins
-  automatically.
+  RTX PRO 6000 recipe needs no changes. On the 32GB RTX 5090 the pins differ per
+  state dtype, and the panel applies them automatically. bfloat16 serves at
+  `--mem-fraction-static 0.88` on the balanced ratio (0.90, DSpark's pin, OOMs
+  on the first request). float32 reaches only the High-Throughput tier, at
+  `--mem-fraction-static 0.895` with `--mamba-full-memory-ratio 10` overriding
+  the balanced value — these cells pin `--max-running-requests 1`, so the
+  balanced ratio provisions KV for concurrency the recipe never uses and
+  starves the state pool of the slots fp32 needs. The Low-Latency tier is
+  greyed out for float32: it needs five fp32 slots plus a full request's KV,
+  and no mem-fraction holds both — buying the fifth slot cuts KV to 7,752
+  tokens against the 9,216 one 8192/1024 request needs, while every
+  mem-fraction with a large enough pool dies in prefill graph capture.
 - **Hardware fit**: FP8 weights ~28.5GB (not serviceable beyond bs≤2 on
  32GB cards); NVFP4 weights ~16.5GB (recommended for RTX 5090-class GPUs).
 - `--mamba-radix-cache-strategy extra_buffer_lazy` lowers the state cost per