[ROCm][Perf] Fix RMSNorm+Quant fusion for gfx950 (non-fnuz) by frida-andersson · Pull Request #41825 · vllm-project/vllm

frida-andersson · 2026-05-06T13:43:45Z

Summary

RocmAiterRMSNormQuantFusionPass was silently skipping the fused AITER RMSNorm+GroupedQuantFP8 kernel on gfx950 (non-fnuz hardware) due to two issues:

matcher_utils.py: MatcherQuantFP8 guarded get_group_quant_op() behind is_fp8_fnuz(). On gfx950 this is False, so the matcher always selected triton_per_token_group_quant_fp8 instead — a different op target that the fusion pattern does not match. Fix: always use get_group_quant_op() when match_rocm_aiter=True.
rocm_aiter_fusion.py: DSv3.2's FX graph has one RMSNorm node feeding multiple downstream quant ops (fan-out). The pattern matcher requires 1-to-1 norm→quant pairs and silently skips multi-consumer norms. Fix: add _dedup_and_duplicate_for_fusion() pre-pass that runs before pattern matching:
- Stage 1 — dedup: collapses identical quant consumers on the same norm (same target + args) into one node.
- Stage 2 — duplicate: clones the norm for each remaining distinct quant consumer so each gets a dedicated 1-to-1 input the pattern matcher can fuse.

Performance

DeepSeek-V3.2 TP4 on MI355X (gfx950), bf16, HIP graphs, block-size 64:

	ms/step
Before	20.69
After	20.01
Delta	-3.3%

Test plan

DeepSeek-V3.2 TP4 bf16 with HIP graphs — GSM8K 5-shot flexible-extract 0.9409 (matches reference)
Server load test: 32 requests, 0 failures, no MAF
Depends on: [ROCm][Bugfix] Fix DeepSeek-V3.2 TP4 sparse MLA with HIP graphs #41760 (correctness fix for DSv3.2 TP4 HIP graphs)

Notes

Co-authored-by: Markus Hartikainen markus.hartikainen@amd.com

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github-actions · 2026-05-06T13:44:05Z

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mergify · 2026-05-06T13:45:03Z

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Code Review

This pull request introduces several optimizations and fixes for ROCm aiter fusion, including a new two-stage graph transformation to deduplicate quantization operations and duplicate RMSNorm nodes for improved fusion matching. It also disables the RocmAiterAllReduceFusionPass to prevent HIP graph replay corruption and removes the UnsafeCloneEliminationPass from the pass manager. Feedback highlights a potential bug in the de-duplication logic where getitem nodes might be erased while still in use, and an inconsistency in the cache UUID generation following the removal of the clone elimination pass.

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vllm/compilation/passes/fusion/rocm_aiter_fusion.py (403-404)

There's a potential issue in the de-duplication logic. If a redundant quant node has a getitem user for an output index that the keep node does not (idx not in keep_gi), the user of that getitem will not be re-parented. Subsequently, graph.erase_node will be called on that getitem node, which will fail if it still has users. You should handle this case by creating a new getitem node on the keep node and replacing uses accordingly before erasing the old getitem node.

vllm/compilation/passes/pass_manager.py (119-120)

By removing the execution of UnsafeCloneEliminationPass, you've introduced an inconsistency with the cache key generation. The uuid() method still includes this pass's UUID (on line 206), which can lead to incorrect cache behavior. To fix this, you should also remove passes.append(self.clone_elimination.uuid()) from the uuid() method.

Two issues prevented RMSNorm+Quant fusion from firing on gfx950: 1. Op mismatch in MatcherQuantFP8: on gfx950 (non-fnuz), the pattern matcher selected triton_per_token_group_quant_fp8 but the model traces rocm_aiter_group_fp8_quant when AITER is enabled. Fix by always using the AITER group quant op for group quantization when match_rocm_aiter=True. 2. Multi-consumer RMSNorm nodes: DeepSeek V3.2 produces FX graphs where a single RMSNorm feeds multiple downstream quant ops, violating the 1-to-1 assumption of the pattern matcher. Add a two-stage pre-pass (_dedup_and_duplicate_for_fusion): - Stage 1 (Dedup): merge identical quant consumers of the same RMSNorm, eliminating redundant computation. - Stage 2 (Duplicate): clone norm nodes for remaining multi-consumer cases so each fusable quant gets a dedicated 1-to-1 norm. Measured on MI355X TP4 with DeepSeek V3.2 (1k/100, conc 4): Recovers 64x _fused_rms_fp8_group_quant_kernel per step Eliminates 61x standalone Rmsnorm2dFwd + 128x standalone quant Total GPU time: 20.69 ms -> 20.01 ms (-3.3%) Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Made-with: Cursor Signed-off-by: Frida Andersson <fanderss@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com>

gshtras · 2026-05-06T19:36:49Z

Do you happen to have some test results (lm_eval) with other models that can use this fusion path?
Would DSR1 and Kimi-K2 be affected?

Rohan138 · 2026-05-06T19:45:21Z

-                    self.QUANT_OP = (
-                        torch.ops.vllm.triton_per_token_group_quant_fp8.default
-                    )
+                self.QUANT_OP = rocm_aiter_ops.get_group_quant_op()


good catch, LGTM

Rohan138 · 2026-05-06T21:28:41Z

+    def _dedup_and_duplicate_for_fusion(graph: fx.Graph) -> tuple[int, int]:
+        """Two-stage graph transform to enable RMSNorm+Quant fusion.
+
+        Stage 1 — Dedup: when the same RMSNorm feeds multiple *identical*


Can you attach the VLLM_DEBUG_DUMP_PATH/TORCH_LOGS=output_code/tlparse results to show the actual graph before and after this? We don't see these duplicate quants on e.g. DSR1/Kimi, I'm not sure where they're coming from. If confirmed, this should ideally be addressed in a separate utility fusion pass e.g. EliminateDuplicateNormQuantPass that runs before the RocmAiterRMSNormQuantFusionPass.

Fresh compile with VLLM_DEBUG_DUMP_PATH=/tmp/graphs, cache cleared.

Pre-fusion: deduped 1 redundant quants, duplicated 0 norms RocmAiterRMSNormQuantFusionPass Replaced 1 patterns [range 1–4681] RocmAiterRMSNormQuantFusionPass Replaced 2 patterns [range 4682–16384]

Source: rms_norm_default_1 (q_c norm, [s72, 1536]) in sparse MLA indexer fans out to two identical rocm_aiter_group_fp8_quant(view, 128) calls (BEFORE_PRE_GRAD.0.py lines 91, 191). DSv3.2-specific, confirmed no-op on Kimi-K2.5 (Replaced 0 patterns).

On EliminateDuplicateNormQuantPass: fair point, could be extracted into a separate pass in the
future

frida-andersson · 2026-05-07T13:49:50Z

Do you happen to have some test results (lm_eval) with other models that can use this fusion path? Would DSR1 and Kimi-K2 be affected?

@gshtras Kimi-K2.5 is not affected — Replaced 0 patterns means the pass found no fusable rms_norm + rocm_aiter_group_fp8_quant patterns in its graph. The fusion is architecturally
irrelevant for this model and cannot affect correctness or performance.

Model	Without patch	With patch	Notes
DeepSeek-V3.2	0.9439	0.9431	fusion active, no regression
Kimi-K2.5	—	0.9310	Replaced 0 — pass is no-op, no patterns present

…sistency Fix two issues flagged in code review: 1. rocm_aiter_fusion.py: In _dedup_and_duplicate_for_fusion, when a redundant quant node has a getitem user for an output index that the keep node does not yet have, graph.erase_node would fail because the getitem still had users. Create a new getitem on the keep node first and redirect uses before erasing. 2. pass_manager.py: Remove passes.append(self.clone_elimination.uuid()) from uuid() to match the fact that UnsafeCloneEliminationPass is no longer executed, fixing the cache key inconsistency. Signed-off-by: Frida Andersson <fanderss@amd.com>

tjtanaa · 2026-05-08T05:06:47Z

Do you happen to have some test results (lm_eval) with other models that can use this fusion path? Would DSR1 and Kimi-K2 be affected?

@gshtras Kimi-K2.5 is not affected — Replaced 0 patterns means the pass found no fusable rms_norm + rocm_aiter_group_fp8_quant patterns in its graph. The fusion is architecturally irrelevant for this model and cannot affect correctness or performance.

Model Without patch With patch Notes
DeepSeek-V3.2 0.9439 0.9431 fusion active, no regression
Kimi-K2.5 — 0.9310 Replaced 0 — pass is no-op, no patterns present

how about DeepSeekV3 (DSR1)?

And since is PR title is Fix RMSNorm+Quant fusion for gfx950 (non-fnuz), how does the change in the dedup behaviour affect the fnuz path?

tjtanaa · 2026-05-08T06:27:24Z


        passes.append(self.post_cleanup.uuid())
        passes.append(self.ir_lowering.uuid())
-        passes.append(self.clone_elimination.uuid())


@frida-andersson @ChuanLi1101

Please make these changes to be gfx950 specific

so it will be

... passes.append(self.clone_elimination.uuid()) if current_platform.is_rocm(): from vllm.platforms.rocm import on_gfx950 if on_gfx950(): passes.pop() ...

IMPORTANT NOTE:

Do not import anything from vllm.platforms.rocm without guarding it with current_platform.is_rocm():. So follow the way I have suggested.

@frida-andersson @ChuanLi1101 why must we remove the clone_elimination? Will it affect dedup?

Note that this doesn't remove the clone elimination from the passes -> it just removes it from the pass key

tjtanaa · 2026-05-08T06:27:55Z

+            )
        self.matched_count = self.patterns.apply(graph)
-        logger.debug(
+        logger.info(


NITS: please revert this, we don't want to have too many logs.

tjtanaa · 2026-05-08T06:28:24Z

+
    @VllmInductorPass.time_and_log
    def __call__(self, graph: fx.Graph) -> None:
+        deduped, duplicated = self._dedup_and_duplicate_for_fusion(graph)


@frida-andersson @ChuanLi1101

Please make these changes to be gfx950 specific

so it will be

... if current_platform.is_rocm(): from vllm.platforms.rocm import on_gfx950 if on_gfx950(): deduped, duplicated = self._dedup_and_duplicate_for_fusion(graph) ...

IMPORTANT NOTE:

Do not import anything from vllm.platforms.rocm without guarding it with current_platform.is_rocm():. So follow the way I have suggested.

good catch @tjtanaa

Done in 90474f7 — gated exactly per your snippet:

deduped, duplicated = 0, 0 if current_platform.is_rocm(): from vllm.platforms.rocm import on_gfx950 if on_gfx950(): deduped, duplicated = self._dedup_and_duplicate_for_fusion(graph)

current_platform was already imported at module level; on_gfx950 is imported only inside the is_rocm() guard as instructed. Pushed to @frida-andersson's branch as collaborator with co-author trailer.

Ready for your re-review / merge whenever convenient. Thanks!

The new declarative DoubleAiterRMSFp8GroupQuantPattern silently no-ops on DSv3.2's MLA indexer q_c norm fan-out: Fp8BlockScaledMMLinearKernel. apply_weights inserts a 2D-flatten between rms_norm and each rocm_aiter_group_fp8_quant, producing the shape rms_norm -> view -> rocm_aiter_group_fp8_quant \-> view -> rocm_aiter_group_fp8_quant while the existing pattern only matches the un-viewed shape. Without this sibling, the ~3.3% delta from vllm-project#41825 on DSv3.2 (TP4 / MI355X / bf16 / HIP graphs / block-size 64) does not actually land. Add DoubleAiterRMSFp8GroupQuantViewPattern that targets the same 1-to-2 fan-out through Inductor's view_to_reshape post-grad pass to unify view -> reshape in both pattern and graph (the same idiom used by QkNormRopePattern). The non-view sibling stays registered alongside to cover fan-out sites without the linear-kernel view (Kimi-K2.5 / DSR1). Adds a small unit test covering both fan-out shapes (rms_norm -> 2x quant and rms_norm -> view -> 2x quant) and asserts each is rewritten into the fused rocm_aiter_rmsnorm_fp8_group_quant op via the corresponding pattern variant. Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Claude Signed-off-by: Chuan Li <chuali@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com>

ChuanLi1101 · 2026-05-09T06:41:46Z

View-tolerant `DoubleAiterRMSFp8GroupQuantViewPattern` pushed (commit `23411808`)

Took option A from @maeehart's follow-up proposal — pushed the view-tolerant sibling as a follow-up commit on this branch rather than stacking. Net diff: +98 / −2 in rocm_aiter_fusion.py, plus a new tests/compile/passes/test_double_aiter_rms_quant_fusion.py.

What's in the commit

DoubleAiterRMSFp8GroupQuantViewPattern — sibling of DoubleAiterRMSFp8GroupQuantPattern that matches the rms_norm -> view -> 2x rocm_aiter_group_fp8_quant shape DSv3.2's MLA indexer q_c norm exposes through Fp8BlockScaledMMLinearKernel.apply_weights's 2D-flatten. Implementation mirrors @maeehart's draft, with two minor structural choices:
- Inlines a 3-line trace_with_view_to_reshape closure inside register() instead of importing QkNormRopePattern.wrap_trace_fn / fx_view_to_reshape. Keeps the cross-pattern coupling to zero (view_to_reshape is imported directly from torch._inductor.fx_passes.post_grad).
- Registered immediately after the no-view DoubleAiterRMSFp8GroupQuantPattern in RocmAiterRMSNormQuantFusionPass.__init__, and added to the uuid() source list so the cache key invalidates correctly.
test_double_aiter_rms_quant_fusion.py — parametrized over both _NoViewDoubleQuantModel and _ViewDoubleQuantModel (DSv3.2 shape). Each shape compiles a tiny module with the target FX graph, runs through RocmAiterRMSNormQuantFusionPass, asserts matched_count == 1, asserts the fused rocm_aiter_rmsnorm_fp8_group_quant op is present after, and includes a numerical parity sanity-check against the unfused output. Skipped on non-ROCm / non-AITER platforms following the is_aiter_found_and_supported() precedent from test_fuse_mla_dual_rms_norm.py.

Why a view-tolerant sibling rather than rolling back #42061

Per @maeehart's note: #42061 is correctness-critical on DSv3.2 at high concurrency (silent gsm8k collapse at num_concurrent=64 without it), so widening this fusion to be view-tolerant is the right architectural fix. The non-view sibling stays registered alongside to cover Kimi-K2.5 / DSR1 fan-out sites that don't sit behind the linear-kernel view.

Asks

@frida-andersson @maeehart — when you're back online, please re-run the DSv3.2 TP4 / MI355X bf16 / HIP graphs / block-size 64 bench against this commit. Expected: the ~3.3% delta from the original PR description should now actually land (was silently no-op'ing per @maeehart's analysis once [ROCm][Bugfix] Re-tag AITER MoE weights as preshuffled after replace_parameter #42061 was applied).
@ProExpertProg — your +1 from this morning ("Yep adding another pattern with the view sounds good!") covers the design; flagging in case you want to skim the implementation before the ready re-trigger.
@tjtanaa — the gfx950 perf signal will land once Frida re-benches.

cc @Akii @dllehr-amd

mergify · 2026-05-09T06:46:24Z

Hi @frida-andersson, the pre-commit checks have failed. Please run:

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Pre-commit ruff/black collapsed the two-line ``self.weight = torch.nn.Parameter(\n torch.ones(HIDDEN_SIZE, ...)\n)`` constructions in ``_NoViewDoubleQuantModel`` and ``_ViewDoubleQuantModel`` to a single line. Pure formatting; no functional change. Signed-off-by: Chuan Li <chuali@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com>

ChuanLi1101 · 2026-05-09T07:59:18Z

Quick status update on the failing checks above, since the mergify warning is a bit misleading:

Pre-commit is green on the latest HEAD. The mergify "pre-commit checks have failed" notice fired against commit 23411808 (the view-tolerant pattern commit). The follow-up commit 00049dbe applied the ruff formatter cleanup it asked for, and the most recent pre-commit run (actions run 25594844619) passed in 3m56s. Mergify doesn't retract its earlier comment automatically, so the warning above is stale.

Only one check is currently red — buildkite/ci/pr/elastic-ep-scaling-test (build #65327). This test exercises elastic Expert-Parallelism rank scaling and is unrelated to this PR's scope (compilation-pass pattern matching for rms_norm + rocm_aiter_group_fp8_quant fusion). The two files this PR touches in the latest commits (vllm/compilation/passes/fusion/rocm_aiter_fusion.py and tests/compile/passes/test_double_aiter_rms_quant_fusion.py) cannot affect that job — the new test itself is gated behind is_aiter_found_and_supported() and won't run in the elastic-EP environment at all.

Waiting on buildkite/ci/pr/pytorch-compilation-passes-unit-tests — that's the job that actually picks up the new test_double_aiter_rms_quant_fusion.py and validates that both _NoViewDoubleQuantModel and _ViewDoubleQuantModel produce matched_count == 1 against the fusion pass. Will report back once it lands.

cc @ProExpertProg @tjtanaa @frida-andersson @maeehart

akii96 · 2026-05-09T10:25:30Z

BTW wrong Akii was tagged above, hopefully he does not mind me answering instead 😆

View-tolerant DoubleAiterRMSFp8GroupQuantViewPattern confirmed firing on DSv3.2 q_c norm fan-out
Cherry-picked commit 2341180 + PR #42061 applied and then re-ran DSv3.2 (Exp) FP8 on MI355X, TP4, bf16, HIP graphs, block-size 64, with VLLM_DEBUG_DUMP_PATH=/tmp/vllm_temp set

BEFORE_PRE_GRAD.0.py — q_c norm fan-out, the shape I diagnosed:

rms_norm_default_1: "bf16[s72, 1536]" = vllm_ir.rms_norm.default(getitem_2, _get_data_attr_1, 1e-06, None)
view_2: "bf16[s72, 1536]" = rms_norm_default_1.view(-1, 1536)   # BlockScaledMMLinearKernel.py:116
rocm_aiter_group_fp8_quant   = vllm.rocm_aiter_group_fp8_quant(view_2, 128)
view_5: "bf16[s72, 1536]" = rms_norm_default_1.view(-1, 1536)   # BlockScaledMMLinearKernel.py:116
rocm_aiter_group_fp8_quant_1 = vllm.rocm_aiter_group_fp8_quant(view_5, 128)

AFTER_POST_GRAD.0.py — collapsed to the fused op:

rocm_aiter_rmsnorm_fp8_group_quant_default = vllm.rocm_aiter_rmsnorm_fp8_group_quant.default(getitem_2, arg6_1, 1e-06, 128)

Same rewrite on all 4 TP ranks: rocm_aiter_group_fp8_quant 6 → 0, rocm_aiter_rmsnorm_fp8_group_quant 0 → 1. The non-view sibling can't have done this (the view is in BEFORE), so it's firmly DoubleAiterRMSFp8GroupQuantViewPattern firing.

lm_eval results:

Tasks	Version	Filter	n-shot	Metric		Value		Stderr
gsm8k	3	flexible-extract	5	exact_match	↑	0.9340	±	0.0068
		strict-match	5	exact_match	↑	0.9067	±	0.0080

TPOT / throughput, same DSv3.2 setup:

vllm bench serve --dataset-name random --port 8000 --model deepseek-ai/DeepSeek-V3.2 --num-prompts 32 --random-input-len 1000 --random-output-len 100 --trust_remote_code --ignore-eos --seed 1 --num_warmups 4 --max_concurrency 4

	Median TPOT (ms)	Output throughput (tok/s)
Without `41825`	24.15	91.76
With `41825`	17.09	101.69
Delta	−29.2%	+10.8%

This looks fantastic! 🚀 Great work all!

cc @ChuanLi1101 @maeehart @frida-andersson @ProExpertProg @tjtanaa @dllehr-amd

The triton vs CK group quant op selection was added speculatively but the approved PR vllm-project#41825 uses only the aiter (CK) group quant op. Align the pattern matching with that decision. Signed-off-by: Tres Popp <tres.popp@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com>

tjtanaa · 2026-05-11T14:15:27Z

@frida-andersson @akii96 is this ready and finalized?

if yes, is it ok to merge? @ProExpertProg

akii96 · 2026-05-11T16:48:04Z

Yeah this was ready and confirmed to fire by me @tjtanaa

ChuanLi1101 · 2026-05-11T18:59:01Z

@tjtanaa Confirmed ready and finalized from our side.

Validation summary:

Pattern firing on real graph: Aakif (@akii96) captured BEFORE/AFTER FX dumps across all 4 TP ranks on DSv3.2 / MI355X / TP4 / bf16 / HIP graphs / block-size 64. The view in the BEFORE dumps rules out the no-view sibling pattern and confirms DoubleAiterRMSFp8GroupQuantViewPattern is the one matching — i.e. the ~3.3% delta this PR claims is actually landing on the gfx950 path, not silently no-oping.
Reviews: @ProExpertProg approved (51502209 + 23411808 + 00049dbe). TJ's earlier asks (gfx950 gating + log levels) are all moot now since the manual graph surgery is gone and replaced by the declarative pattern.
CI on 5d264f00: buildkite/ci/pr ✅ pass, buildkite/amd-ci ✅ pass, pre-commit ✅, DCO ✅, docs ✅. mergeStateStatus: CLEAN.

Good to merge whenever convenient. @ProExpertProg — final green light from you and TJ can land it.

ProExpertProg

Great job cleaning up and thanks for the clarifications!

…ject#41825) Signed-off-by: Frida Andersson <fanderss@amd.com> Signed-off-by: Chuan Li <chuali@amd.com> Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com> Co-authored-by: Chuan Li <chuali@amd.com> Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com> Co-authored-by: Frida Andersson <frida-andersson@users.noreply.github.com> Co-authored-by: TJian <tunjian.tan@embeddedllm.com>

DSv3.2 (and other FP8-blockwise models) end every transformer block with all_reduce -> [fused_add_]rms_norm -> rocm_aiter_group_fp8_quant -> fp8_gemm PR vllm-project#41825 fixed the quant-side half of this (`RocmAiterRMSNormQuantFusionPass`) so a plain `rms_norm -> group_fp8_quant` pair is rewritten as `rocm_aiter_rmsnorm_fp8_group_quant` (one HIP call). But that pass cannot fire when the `rms_norm` consumer of the all_reduce has already been absorbed by `RocmAiterAllReduceFusionPass`: at that point the FX graph just sees an opaque `rocm_aiter_fused_allreduce_rmsnorm` producing bf16 and the standalone `rocm_aiter_group_fp8_quant` consumer stays unfused. On a DSv3.2 TP4 decode trace that leaves ~535us / step of `dynamic_per_group_scaled_quant` launches (122 calls per step at ~4.4us each). This change extends `RocmAiterAllReduceFusionPass` with two new patterns that match the full `AR -> RMSNorm[+add] -> group_fp8_quant` chain and rewrite it into a single `rocm_aiter_fused_allreduce_rmsnorm_quant_per_group` op backed by AITER's `fused_ar_rms_per_group_quant` launcher (ROCm/aiter PR vllm-project#2823). Mechanics: - `vllm/_aiter_ops.py`: add the custom op binding plus the `AiterCustomAllreduceProto` member, a fake impl returning the FP8 quant tensor + per-group scale (`(M, hidden/group_size)` float32), and a feature- probe `has_fused_allreduce_rmsnorm_quant_per_group` so callers can degrade cleanly on older aiter builds. - `vllm/compilation/passes/fusion/allreduce_rms_fusion.py`: two new `VllmPatternReplacement` patterns (`AiterAllreduceFusedRMSNormGroupQuantFP8Pattern` and the `fused_add` sibling) wired into `RocmAiterAllReduceFusionPass`. Both reuse `MatcherQuantFP8` to be insensitive to whether `quant_fp8` is enabled as a custom op (same approach as PR vllm-project#41825). The quant variants register before the non-quant variants so the matcher prefers them whenever a downstream group quant exists; the existing AR+RMS-only patterns still match for the AR sites that lack a trailing quant (e.g. final block). - The pass keys off `rocm_aiter_ops.has_fused_allreduce_rmsnorm_quant_per_group()` so an aiter build without PR vllm-project#2823 silently falls back to the existing AR+RMS-only fusion (correct but slower). This is the AR-side analogue of PR vllm-project#41825 and the ROCm port of the flashinfer `AllReduceFusedRMSNormStaticQuantFP8Pattern` family that already exists in the same file for the NVIDIA path. Validation pending: needs DSv3.2 TP4 bf16-rms-bf16-input FP8-blockwise smoke on MI355X to confirm pattern count and end-to-end serving accuracy parity. Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com> Signed-off-by: Markus Hartikainen <markus.hartikainen@amd.com>

…ject#41825) Signed-off-by: Frida Andersson <fanderss@amd.com> Signed-off-by: Chuan Li <chuali@amd.com> Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com> Co-authored-by: Chuan Li <chuali@amd.com> Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com> Co-authored-by: Frida Andersson <frida-andersson@users.noreply.github.com> Co-authored-by: TJian <tunjian.tan@embeddedllm.com>

DSv3.2 (and other FP8-blockwise models) end every transformer block with all_reduce -> [fused_add_]rms_norm -> rocm_aiter_group_fp8_quant -> fp8_gemm PR vllm-project#41825 fixed the quant-side half of this (`RocmAiterRMSNormQuantFusionPass`) so a plain `rms_norm -> group_fp8_quant` pair is rewritten as `rocm_aiter_rmsnorm_fp8_group_quant` (one HIP call). But that pass cannot fire when the `rms_norm` consumer of the all_reduce has already been absorbed by `RocmAiterAllReduceFusionPass`: at that point the FX graph just sees an opaque `rocm_aiter_fused_allreduce_rmsnorm` producing bf16 and the standalone `rocm_aiter_group_fp8_quant` consumer stays unfused. On a DSv3.2 TP4 decode trace that leaves ~535us / step of `dynamic_per_group_scaled_quant` launches (122 calls per step at ~4.4us each). This change extends `RocmAiterAllReduceFusionPass` with two new patterns that match the full `AR -> RMSNorm[+add] -> group_fp8_quant` chain and rewrite it into a single `rocm_aiter_fused_allreduce_rmsnorm_quant_per_group` op backed by AITER's `fused_ar_rms_per_group_quant` launcher (ROCm/aiter PR vllm-project#2823). Mechanics: - `vllm/_aiter_ops.py`: add the custom op binding plus the `AiterCustomAllreduceProto` member, a fake impl returning the FP8 quant tensor + per-group scale (`(M, hidden/group_size)` float32), and a feature- probe `has_fused_allreduce_rmsnorm_quant_per_group` so callers can degrade cleanly on older aiter builds. - `vllm/compilation/passes/fusion/allreduce_rms_fusion.py`: two new `VllmPatternReplacement` patterns (`AiterAllreduceFusedRMSNormGroupQuantFP8Pattern` and the `fused_add` sibling) wired into `RocmAiterAllReduceFusionPass`. Both reuse `MatcherQuantFP8` to be insensitive to whether `quant_fp8` is enabled as a custom op (same approach as PR vllm-project#41825). The quant variants register before the non-quant variants so the matcher prefers them whenever a downstream group quant exists; the existing AR+RMS-only patterns still match for the AR sites that lack a trailing quant (e.g. final block). - The pass keys off `rocm_aiter_ops.has_fused_allreduce_rmsnorm_quant_per_group()` so an aiter build without PR vllm-project#2823 silently falls back to the existing AR+RMS-only fusion (correct but slower). This is the AR-side analogue of PR vllm-project#41825 and the ROCm port of the flashinfer `AllReduceFusedRMSNormStaticQuantFP8Pattern` family that already exists in the same file for the NVIDIA path. Validation pending: needs DSv3.2 TP4 bf16-rms-bf16-input FP8-blockwise smoke on MI355X to confirm pattern count and end-to-end serving accuracy parity. Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com> Signed-off-by: Markus Hartikainen <markus.hartikainen@amd.com>

…ject#41825) Signed-off-by: Frida Andersson <fanderss@amd.com> Signed-off-by: Chuan Li <chuali@amd.com> Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com> Co-authored-by: Chuan Li <chuali@amd.com> Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com> Co-authored-by: Frida Andersson <frida-andersson@users.noreply.github.com> Co-authored-by: TJian <tunjian.tan@embeddedllm.com> Signed-off-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

…ject#41825) Signed-off-by: Frida Andersson <fanderss@amd.com> Signed-off-by: Chuan Li <chuali@amd.com> Co-authored-by: Markus Hartikainen <markus.hartikainen@amd.com> Co-authored-by: Cursor <cursoragent@cursor.com> Co-authored-by: Chuan Li <chuali@amd.com> Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com> Co-authored-by: Frida Andersson <frida-andersson@users.noreply.github.com> Co-authored-by: TJian <tunjian.tan@embeddedllm.com>

frida-andersson requested review from BoyuanFeng, ProExpertProg, tjtanaa, vadiklyutiy, youkaichao and zou3519 as code owners May 6, 2026 13:43

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frida-andersson force-pushed the pr/rmsnorm-quant-fusion-gfx950 branch from dce794c to 0f0eb1d Compare May 6, 2026 13:48

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frida-andersson force-pushed the pr/rmsnorm-quant-fusion-gfx950 branch from 8c15cbd to 90a1332 Compare May 7, 2026 14:37

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Merge branch 'main' into pr/rmsnorm-quant-fusion-gfx950

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maeehart mentioned this pull request May 11, 2026

[ROCm][MLA] FP8 ASM prefill on gfx950 for AITER MLA backend #42294

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ProExpertProg merged commit a721315 into vllm-project:main May 11, 2026
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maeehart mentioned this pull request May 17, 2026

[ROCm][Compile] Fuse AR + RMSNorm + per-group FP8 quant (+ DSv3.2 indexer fan-out) #42864

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functionstackx mentioned this pull request May 19, 2026

[Bug][Perf] MiniMax-M2.5 FP8 on MI325X — ~38% throughput regression between vLLM ROCm v0.18.0 and v0.21.0 #43029

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vllm/compilation/passes/fusion/rocm_aiter_fusion.py (403-404)

vllm/compilation/passes/pass_manager.py (119-120)

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ChuanLi1101 commented May 9, 2026

View-tolerant DoubleAiterRMSFp8GroupQuantViewPattern pushed (commit 23411808)

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Why a view-tolerant sibling rather than rolling back #42061

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View-tolerant `DoubleAiterRMSFp8GroupQuantViewPattern` pushed (commit `23411808`)

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