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[Perf][Qwen4Exp] Add SM121 TP=2 merged QSA projection plans - #61437
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After vllm-project#59533 merged the QSA QKV/gate projection with the replicated indexer Q/K projection, the TP=2 local weight on DGX Spark (SM121) is (7296, 2560). QWEN4_EXP_SM121_GEMM_PLANS only had the TP=1 merged shape (13952, 2560) and the pre-merge TP=2 shape (6656, 2560) from vllm-project#59632, so on a 2x DGX Spark TP=2 deployment every QSA projection call fell back to cuBLAS (gemvx at M=1, cutlass_80_wmma at M=2..16). Add the measured (7296, 2560) rows for M=1/2/4/8/16 (GB10, cold L2: about 1.5x at M=1 and 1.05x-1.15x at M=2..16 vs cuBLAS, cosine 0.999999 vs FP32 F.linear) and keep the (6656, 2560) row for the LoRA path, which does not fuse the indexer projection. Signed-off-by: TimRen01 <HolaTim@hotmail.com>
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✅ Triggered Buildkite CI #94514 for commit |
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✅ @TimRen01, CI is now available for this PR.
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…ject#61437) Signed-off-by: TimRen01 <HolaTim@hotmail.com> Co-authored-by: Thien Tran <gau.nernst@yahoo.com.sg> Signed-off-by: Andreas Karatzas <AndreasKaratzas@users.noreply.github.com>
…ject#61437) Signed-off-by: TimRen01 <HolaTim@hotmail.com> Co-authored-by: Thien Tran <gau.nernst@yahoo.com.sg>
Overview
#59533 merged the QSA QKV/gate projection with the replicated indexer Q/K projection, so at TP=2 on DGX Spark
(GB10, SM121) the local weight is
(7296, 2560)= 6656 + 640.QWEN4_EXP_SM121_GEMM_PLANShas the TP=1 mergedshape
(13952, 2560)but not the TP=2 one, so on a 2x DGX Spark TP=2 deployment every QSA projection call fallsback to cuBLAS. This PR adds the measured
(7296, 2560)rows for M = 1/2/4/8/16 and keeps(6656, 2560)for theLoRA path, which does not fuse the indexer projection.
Claims
(7296, 2560)BF16, cold L2, fresh process, arms alternated: at M=1 the skinny kernel reads the weight atabout 250 GB/s vs 165 GB/s for the cuBLAS
gemvxkernel (~1.5x). At M=2..16 cuBLAS already reaches225-235 GB/s, so the gain is about 1.05x-1.15x. Cosine 0.999999 vs FP32
F.linearfor every row.gemvx(218 us, M=1) /cutlass_80_wmma(170 us, M=2/4) to the planned skinny kernel (162 us): 2.57 -> 2.35 ms per decode step.Like [Perf][Qwen4Exp] Keep the HC up projection on the skinny GEMM path #60027, this PR restores a planned dispatch path; it does not claim an end-to-end speedup (see Validation).
Validation
All measurements are on 2x NVIDIA DGX Spark (GB10, SM121, driver 580.178.04), TP=2 over ConnectX-7 200G RoCE,
image
vllm/vllm-openai:nightly-5555a2d8f7116b2b4877f66516f4128176cf722a(vLLM 0.31.1rc1.dev376,torch 2.13.0+cu130, FlashInfer 0.7.0.post1, cutlass 4.8.0, Ny contains #59533, #59632
and #60027; its
low_latency_gemm.pyis byte-identical to tThe PR arm is the sameimage with this file overlaid. Host: `vm.compaction_proactivure scripts and the raw
result files are in this gist: .
Kernel (committed rows vs cuBLAS; fresh process, no otheed cuBLAS / skinny /
skinny / cuBLAS, 10 rounds x 50 graph-replayed launches, 8 rB > L2, median):
Row selection: every valid
SkinnyGemmConfig(block 32..256l 1..4, vector width2..8, static K on/off; 108 candidates per M) was timed once n of 5). The best
candidates were 142 / 142 / 141 / 142 / 148 us at M = 1/2/4/the same kernels with
k_unrolldropped, because withstatic_kthe K loop is fuas no effect.Single-run sweep timings of identical kernels differ by up tat M=2), which is why
the table above re-measures the committed rows instead of qu numbers.
Serving trace (nsys, both nodes; 229 decode steps on maiws
gemvxgrid 1824(= 7296 / 4) and
cutlass_80_wmmagrid (8, 57) (= ceil(7296isappear and the skinnykernel runs at grid 7296. CuTeDSL warmup compile units 42 ->ojection on rank 0:
2.567 -> 2.345 ms.
Tests (GB10):
pytest tests/kernels/test_bf16_skinny_gem, 48 skipped (the skips are other-architecture cases; the unpatched image givews run through the existingQWEN4_EXP_SM121_CASESparametrization astest_qw[7296-2560-{1,2,4,8,16}-*]and PASSED; no test file is changed. Two early-k 7296invocations, made while a vLLM server was holding most of the unified memory on the same GPU, reported failures whose selection then passed in 3 isolated runs, 1 run concurrent with a kernel sweep, and 2her CUDA process, so we attribute them to the memory-pressure environment rather tharuff format --check`clean on the file.
End to end,
RadixArk/Qwen3.8-Flash-Next-NVFP4, TP=2, M 0.80, SPEED-Benchthroughput_2k(HLE rows excluded), 2K in / 1K out, `--ignoPR -> base, two runs perarm (raw JSON in the gist):
| arm / run | c=1 tok/s | c=1 ITL p50 (ms) | c=1 AL | c=8 to
|---|---:|---:|---:|---:|---:|
| base run 1 | 35.42 | 55.86 | 2.04 | 119.97 | 121.26 |
| PR run 1 | 37.05 | 54.39 | 2.08 | 122.46 | 120.99 |
| PR run 2 | 36.75 | 54.28 | 2.05 | 124.32 | 120.83 |
| base run 2 | 35.73 | 56.13 | 2.09 | 114.89 | 125.15 |
The c=1 direction is consistent (ITL p50 56.0 -> 54.3 ms), battribute only about
0.22 ms per step to this projection; the rest of the differeace level (NCCL wait time
and other kernels also moved between the two runs) and is trof the two-node setup.
The two c=8 base runs differ by more than the PR effect. We -to-end speedup. GSM8K
(100 questions, thinking on, temperature 0, c=8): base 94, P
Details
Root cause:
_qwen4_exp_low_latency_gemmandenable_qwen4_(weight.shape[0], weight.shape[1]);Qwen4ExpQSAQKVIndexeroutput_sizes = [*qkv, index_size * tp_size], so the TP=2 w matches, with no logline (the layer keeps
UnquantizedLinearMethod, so no warmu(13952) and the TP=4tables (4224) were already covered.
Not a duplicate: after #59632 the only change to this file io open PR or issue
covers the TP=2 merged shape (searched 2026-10-13). Related:9753 (TP=1 table),
#59632 (TP=2 table), #59533 (projection merge), #60027 (HC u
Pull Request Checklist
I used vLLM's
/pr-checklistskill.AI assistance was used during the creation of this PR s and this description);
all numbers were measured on the hardware above.
Design Fit: data-only change to the existing SM121patch changes.
Testing and Validation: covered by the existing `Qrization; kernel, trace
and end-to-end data above.
Code Quality and Style:
ruff checkand `ruff forPull Request Contents: root cause, coordination win and remaining caveats.