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[SM90] MegaMoE: fix workspace cleanup; enable push dispatch on H200; support other models - #6517
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…anup Single-dispatch-warp plans fetch the per-expert counts only in warp 0, but cleanup_workspace() runs on every dispatch warp and derives pool block offsets from each warp's cached counts. Warp 1 used offset 0, so blocks 32+ of every local expert except expert 0 kept stale L1 arrival counts / L2 masks and the next launch failed (H20, M 97..128, one expert > 32 BM24 blocks, e.g. CUDA graph capture). Let inactive dispatch warps fetch the final counts before cleanup. Adds test_hot_expert_workspace_cleanup (hot routing, M=97/128, repeated calls and CUDA graph replay): fails before the fix on 8xH20, passes after (41 passed). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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The counter policy only had H20 buckets, so H200 always took the pull path with NVLink barrier #1. Add measured H200 EP8 buckets: push for M 1..32 on the V4-Flash (H4096/E256/K6) and MiMo (H6144/E384/K8) geometries, and push for M 1..64 with the rotated pool for M 33..64 on Pro (H7168/E384/K6). Push removes ~10 us per call: 1.03-1.16x kernel time at the enabled M on 8xH200 across uniform, Zipf-skewed and hot-experts-on-one-rank routers; each bound is the largest M that does not lose on any of them (push loses at BM64, 0.89-0.95x at M=256). Outputs stay bitwise identical to pull. H20 and EP4 policies are unchanged. Adds test_h200_ep8_counter_policy (CPU). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Counter dispatch:
- Allow push / rotated pool only on the validated small-M plans (M <= 64,
BLOCK_M <= 24) and when the push row copy supports the hidden size
(hidden % 1024 == 0); force_* overrides outside that range fall back to the
barrier path (forced push at BM64 could produce run-to-run differences).
- Geometries without measured buckets push (without the rotated pool) up to
M = 32 on H20 and H200.
Untuned geometries (e.g. DeepSeek-V3 H7168/E256/K8, Kimi-K2 H7168/E384/K8):
- The H20 tile buckets assume the RS arm of the three tuned geometries; match
them on (hidden, experts, top-k) instead of hidden alone. Before, any other
geometry with the same hidden got 6 stages without RS and failed to compile
("Unexpected SM90 pipeline depth", shared-memory capacity).
- Replace the Pro-only BLOCK_M=8 stage clamp with the shared-memory budget the
4-stage layout leaves for the expert-count table and dispatch send rows;
H7168/E384 (Kimi-K2) and H >= 7680 no longer overflow at M <= 16.
- Reject shapes the kernel cannot compile (hidden alignment, intermediate not a
multiple of 128 or larger than hidden / 2) with a ValueError.
Plans of the three tuned geometries are unchanged on H20/H200, EP4/EP8,
M 1..256. 198 distinct fused/split plans of six untuned geometries compile;
Kimi-K2 and DeepSeek-V3 shapes pass the reference check on 8xH200 (fused
M 1..128 random/hot routing, split M 384/1024).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The NVFP4 fused plan only accepted 32/48 local experts at EP8 (64/96 at EP4), the counts of the tuned models, although the kernels handle the expert count generically (per-lane expert caches, SM-strided cleanup, C++-sized split plan). Remove that restriction; GLM-4.5/4.6/4.7 (E128/E160), Qwen3 (E128) and Qwen3-Next / Qwen3.5-397B (E512) now select a plan. Push dispatch publishes local expert e from SM e, so it additionally requires experts per rank <= SMs. 192 distinct fused/split plans of the GLM / Qwen geometries compile (H20/H200, EP4/EP8). On 8xH200 the GLM-4.7 (EP8, EP4), GLM-4.5-Air, Qwen3-30B and Qwen3.5-397B shapes pass the reference check (fused M 1..128, random/hot routing; split M=384). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Inline comments:
Review comments at @flashinfer/megamoe/heuristics.py:
- Line 344: Update `select_fused_plan` to validate the complete shared-memory
layout for the selected tile and stage configuration against `SMEM_CAPACITY`
before returning or compiling a plan. Reject configurations that exceed the
limit or select a fitting schedule; apply this check to generic plans, not only
the existing `BLOCK_M=8` adjustment.
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Review comments at @flashinfer/megamoe/weights.py:
- Around line 182-195: In the gated `[E, 2]` branch of the weight-scale folding
logic, validate that the ratio-adjusted local scales remain exactly
representable in E4M3 before applying the power-of-two shift; raise a
gate/up-specific error if folding is lossy, rather than allowing the later
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docs/api/megamoe.rstflashinfer/megamoe/__init__.pyflashinfer/megamoe/heuristics.pyflashinfer/megamoe/weights.pytests/moe/test_megamoe_fp4_sm90.pytests/moe/test_megamoe_fp4_weights.py
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State in the weight-preparation docs what callers convert before the transforms: Marlin byte order (checkpoints are usually low-nibble-first), the decoder scale ranges (NVFP4 6 * scale <= 448; MXFP4 2^-5..2^6 for groups with nonzero codes, else silent saturation or flush), and per-expert global scales passed at run time. The module usage example shows the full flow. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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prewarm() builds every NVFP4 module nvfp4_mega_moe can select up to the buffer capacity, sharded across ranks, so frameworks need not reach into the JIT internals before CUDA graph capture. commit_staged() marks rows a producer wrote directly into the now-documented staging views (x, x_sf, topk_idx, topk_weights), replacing writes to num_staged_tokens. The kernel and stage() paths are unchanged. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The fused kernel keeps a per-expert count table in shared memory, so its footprint grows with the expert count; at 8192 experts the generic BM64 3-stage plan needs 236576 B and failed the kernel static assert. The planner now computes the whole fused layout (mirroring sm90_nvfp4_mega_moe_fused_body.inl) and falls back to BM8 3-stage or the next smaller legal tile when the chosen one does not fit, raising ValueError if none does. This replaces the BM8-only headroom check; plans of the tuned and previously validated geometries are unchanged. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Inline comments:
Review comments at @flashinfer/megamoe/heuristics.py:
- Around line 418-427: The push-plan selection around the capacity check must be
collective: validate equal num_tokens across ranks or derive a cross-rank bound,
then use the same push, no_clean, and BLOCK_M decisions on every rank. Update
nvfp4_mega_moe, MegaMoESymmBuffer.stage, and commit_staged documentation to
state this requirement.
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flashinfer/megamoe/__init__.pyflashinfer/megamoe/heuristics.pyflashinfer/megamoe/weights.pytests/moe/test_megamoe_fp4_ep.pytests/moe/test_megamoe_fp4_sm90.py
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The fused plan (family, tile, push dispatch) is selected from num_tokens and every rank must launch the same kernel, so state on nvfp4_mega_moe, mxfp4_mega_moe, MegaMoESymmBuffer.stage and commit_staged that the token count must match across ranks, with short ranks padded by rows routed to -1. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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@flashinfer-bot run tests/moe/test_megamoe_fp4_sm90.py tests/moe/test_megamoe_fp4_ep.py |
📌 Description
Follow-up to #6343 (SM90 FP4 MegaMoE):
single_active_dispatch_warp, the inactive dispatch warp cleaned the workspace with empty expert counts and left pool blocks ≥ 32 of hot experts stale, so the next launch failed (H20, 97–128 tokens per rank, e.g. CUDA-graph capture); it now fetches the counts first (outputs bitwise unchanged, timing within noise).ValueError), and allow push only on validated plans, so Kimi-K2, DeepSeek-V3, GLM-4.x and Qwen3 shapes now run correctly while plans of the three tuned geometries are unchanged.transform_{nvfp4,mxfp4}_weights_for_mega_moe: Marlin byte order (checkpoints are usually low-nibble-first), scales inside the decoder range (NVFP46 * scale <= 448; MXFP42^-5–2^6for groups with nonzero codes, otherwise outputs silently saturate or flush), and the excess moved into per-expert global scales passed at run time; the module example shows the full flow.MegaMoESymmBuffer.prewarm(), which builds every NVFP4 modulenvfp4_mega_moecan select up to capacity (sharded across ranks, before CUDA graph capture), andcommit_staged(), which accepts rows a producer wrote directly into the now-documented staging views (x,x_sf,topk_idx,topk_weights), so integrations no longer reach into JIT internals or buffer fields.How to use: FlashInfer only provides the kernels and the layout transforms; frameworks convert checkpoint tensors to the format above at load time, call
prewarm()once, and stage inputs withstage()or in place pluscommit_staged()(the SGLang integration does this fornvidia/DeepSeek-V4-Flash-NVFP4, where about 51% of blocks would saturate without rebalancing).🔍 Related Issues
Follow-up to #6343.
🚀 Pull Request Checklist
✅ Pre-commit Checks
pre-commitby runningpip install pre-commit(or used your preferred method).pre-commit install.pre-commit run --all-filesand fixed any reported issues.🧪 Tests
Tests have been added or updated as needed.
All tests are passing (
unittest, etc.).test_hot_expert_workspace_cleanupreproduces fix 1: it fails before the fix on 8×H20 and passes after.New CPU tests cover the H200 buckets, the counter-dispatch limits and plan legality for other geometries, including 2048 and 8192 experts (every plan fits shared memory); every fused and split plan selected for 12 geometries (the three tuned models, six common shapes, 1024 / 2048 / 8192 experts) compiles on SM90, and plans of the tuned and previously validated geometries are unchanged.
test_nvfp4_prewarm_and_direct_stagingchecks that afterprewarm()no fused or split call compiles a new module, that in-place staging pluscommit_staged()gives correct results under CUDA graphs, and that out-of-range counts are rejected.tests/moe/test_megamoe_fp4_{sm90,ep,weights}.py: 73 passed on 8×H200.Reviewer Notes
Summary by CodeRabbit
New Features
Bug Fixes
Documentation