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[TRTLLM-14024][feat] Prune CuTe DSL GEMM autotuner tactics with nvMatmulHeuristics - #19326

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@peaceh-nv peaceh-nv commented Sep 17, 2026

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Add nvMatmulHeuristics (nvMMH) support for Rubin CuTe DSL NVFP4, MXFP8 blockscale and BF16 GEMMs

Summary

  • Integrate nvMMH into CuTe DSL tactic generation so modeled tactic fields can
    be ranked and pruned before JIT compilation and profiling.
  • Cover Blackwell and Rubin dense NVFP4, FP8/MXFP8, and BF16 GEMM runners while
    preserving each runner's validated local tactic variants.
  • Keep nvMMH opt-in and fail open to the full sweep when the library is
    unavailable or returns no usable match.

Enabling nvMMH

nvMMH is disabled by default. For the PyTorch LLM API, add the policy to an
extra_llm_api_options.yaml file. The presence of an
autotuner_nvmmh_config mapping enables nvMMH; omission or null keeps the
full sweep.

enable_autotuner: true
autotuner_nvmmh_config:
  fields: [swizzle, cta_order, split_k]
  max_tactics: 5

For direct Python use, install one complete, immutable NvMMHConfig before
model loading and tactic enumeration:

from tensorrt_llm._torch.autotuner import AutoTuner, NvMMHConfig

AutoTuner.get().configure_nvmmh(
    NvMMHConfig(
        enabled=True,
        fields=("swizzle", "cta_order", "split_k"),
        max_tactics=5,
    )
)

Modeled fields by runner

The five canonical fields are tile, cluster, swizzle, cta_order, and
split_k. Selecting either tile or cluster selects both because nvMMH
models them jointly.

Arch Precision Modeled fields
SM100/SM103 NVFP4 tile, cluster; swizzle, cta_order
SM100/SM103 blockwise FP8 tile, cluster
SM100/SM103 BF16 all five
SM107 (Rubin) block-scaled NVFP4 all five
SM107 (Rubin) block-scaled MXFP8 all five
SM107 (Rubin) per-tensor FP8 tile, cluster, cta_order
SM107 (Rubin) BF16 all five

Autotuner timing

CuteDSLTunableRunner is a marker subclass that selects the timing policy; the
shared AutoTuner still owns warmup, profiling, winner selection, fallback,
and cache management.

Behavior Plain TunableRunner Direct CuteDSLTunableRunner
Preferred measurement Existing %globaltimer or CUDA-event path torch.profiler CUDA activities through Kineto/CUPTI
What is measured Legacy event/timer interval Sum of positive CUDA activity durations across launches, including auxiliary streams, divided by the launch count
Synchronization Existing runner/stream synchronization Device-wide synchronization before closing the profiler
CUPTI unavailable Not applicable; CUPTI is not requested Latch the failure process-wide and fall back to CUDA events
Failure during a sweep Existing behavior Discard mixed CUPTI/event measurements and repeat the complete candidate sweep with CUDA events
Profiling-cache identity Legacy cache-key shape Separate torch_profiler and cuda_event_fallback discriminator

Tests

  • Add unit coverage for FP8/BF16 ranking and filtering, rank-1 split-K, local
    tactic preservation, CTA-order mapping, CUDA-graph/eager CUPTI fallback, cache
    separation, kernel-error preservation, and subprocess timer propagation.
  • Add SM107 correctness/performance comparisons for NVFP4, FP8 4096³, and BF16
    [16,7168] x [7168,256], plus a torch.profiler benchmark of scheduler-only
    nvMMH versus the full BF16 sweep for the transposed
    [16384,7168] x [7168,2112] weight shape.

Workload

  • DeepSeek V4 Pro, generation-only
  • MTP disabled
  • 2 nodes x 4 GPUs
  • TP8 / EP8 / ADP8
  • Local maximum batch size: 32
  • Concurrency: 256
  • Requests: 2,560
  • Input/output lengths: 1,024 / 1,024
  • CuTe DSL block-scaled MXFP8 GEMM enabled
  • Scheduler-only nvMMH fields: [swizzle, cta_order, split_k]
  • CTA tile and cluster shape remained in the autotuner sweep

Autotuner Results

Metric Full sweep Scheduler-only nvMMH Change
Cold autotune time 1,152 s 234 s -79.69% (4.92x faster)
Autotune time saved - 918 s 15m18s saved

Serving Performance Results

Change is scheduler-only nvMMH relative to full sweep. Lower is better for latency and duration metrics; higher is better for throughput.

Metric Full sweep Scheduler-only nvMMH Change
Output throughput 11,712.87 tok/s 11,568.83 tok/s -1.23%
Request throughput 11.438 req/s 11.298 req/s -1.22%
Benchmark duration 223.81 s 226.60 s +1.25%
Mean TTFT 155.95 ms 147.51 ms -5.41%
P99 TTFT 1,054.80 ms 925.46 ms -12.26%
Mean TPOT 21.706 ms 21.982 ms +1.27%
P99 TPOT 22.174 ms 22.313 ms +0.63%
Mean ITL 427.02 ms 432.45 ms +1.27%
P99 ITL 456.60 ms 485.47 ms +6.32%
Mean E2EL 22,361.00 ms 22,635.10 ms +1.23%
P99 E2EL 23,313.04 ms 23,557.67 ms +1.05%

Description

Test Coverage

PR Checklist

Please review the following before submitting your PR:

  • PR description clearly explains what and why. If using CodeRabbit's summary, please make sure it makes sense.

  • PR Follows TRT-LLM CODING GUIDELINES to the best of your knowledge.

  • Test cases are provided for new code paths (see test instructions)

  • If PR introduces API changes, an appropriate PR label is added - either api-compatible or api-breaking. For api-breaking, include BREAKING in the PR title.

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  • CODEOWNERS updated if ownership changes

  • Documentation updated as needed

  • Update tava architecture diagram if there is a significant design change in PR.

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  • Please check this after reviewing the above items as appropriate for this PR.

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Dev Engineer Review

  • Adds optional nvMatmulHeuristics support for CuTe DSL GEMM tactic ranking and pruning on Blackwell and Rubin.
  • Keeps nvMMH disabled by default and falls back to full tactic sweeps when unavailable or unmatched.
  • Adds Python and LLM API configuration through NvMMHConfig and AutoTunerNvMMHConfig.
  • Separates tactic-search and profiling-timer cache identities.
  • Adds CUPTI profiling with CUDA-event fallback and mixed-timer recovery.
  • Preserves validated local tactics and adds raster, swizzle, TMA-store, and split-K metadata.
  • Main risks are cache isolation, profiler fallback, split-K admission, and cross-SM compatibility.
  • Reported cold autotuning time decreased from 1,152 seconds to 234 seconds. Reported throughput changed by approximately -1.2%.

QA Engineer Review

  • test_autotuner.py adds coverage for nvMMH ranking, fallback, policy lifetime, replay, split-K, kernel errors, correctness, and performance across BF16, MXFP8, and NVFP4.
  • test_fp8_block_scale_gemm.py adds Rubin MXFP8 coverage for swizzle, raster order, split-K, numerical correctness, and replay.
  • tests/unittest/api_stability/references/llm.yaml adds the prototype autotuner_nvmmh_config API entry.
  • No test-list files changed.
  • Test-list registration for the changed tests is not established from the supplied evidence.
  • Coverage verdict: needs follow-up because test execution status and test-list registration are not supplied.

Per-File QA Perspective

  • docs/source/torch/adding_custom_kernels.md: Verify documented nvMMH defaults, policy ownership, fallback behavior, and split-K rules.
  • examples/layer_wise_benchmarks/README.md: Verify documented YAML configuration and disablement behavior.
  • examples/layer_wise_benchmarks/config_ctx.yaml: Verify configured fields and tactic limit.
  • examples/layer_wise_benchmarks/config_gen.yaml: Verify configured fields and tactic limit.
  • examples/layer_wise_benchmarks/run.py: Verify parsing, defaults, and configuration ordering.
  • tensorrt_llm/_torch/autotuner.py: Verify policy validation, cache separation, CUPTI fallback, and mixed-timer recovery.
  • tensorrt_llm/_torch/custom_ops/cute_dsl_custom_ops.py: Verify runner migration, tactic pruning, local-tactic preservation, and split-K behavior.
  • tensorrt_llm/_torch/custom_ops/cutedsl_matmul_heuristics.py: Verify model filtering, CTA-order conversion, split expansion, and fallback.
  • tensorrt_llm/_torch/custom_ops/torch_custom_ops.py: Verify profiler selection and tactic-search cache keys.
  • tensorrt_llm/_torch/cute_dsl_kernels/rubin/dense_bf16_gemm_persistent.py: Verify unique kernel names for scheduling variants.
  • tensorrt_llm/_torch/locality_domain/autotune.py: Verify wrapped runner cache-key propagation.
  • tensorrt_llm/_torch/moe/fused_moe/fused_moe_cute_dsl.py: Verify fused MoE integration with the CuTe DSL tuning path.
  • tensorrt_llm/_torch/pyexecutor/model_engine.py: Verify policy acquisition before model loading and release during cleanup.
  • tensorrt_llm/llmapi/__init__.py: Verify public export of AutoTunerNvMMHConfig.
  • tensorrt_llm/llmapi/llm_args.py: Verify validation, canonical ordering, tile/cluster coupling, and None disablement.
  • tensorrt_llm/usage/llm_args_golden_manifest.json: Verify API schema entries for the new fields.
  • tests/unittest/_torch/misc/test_autotuner.py: Verify nvMMH ranking, fallback, policy lifetime, correctness, replay, and performance. No test-list file changed for this test.
  • tests/unittest/_torch/thop/parallel/test_fp8_block_scale_gemm.py: Verify Rubin MXFP8 scheduling, split-K, correctness, and replay. No test-list file changed for this test.
  • tests/unittest/api_stability/references/llm.yaml: Verify API stability for the new prototype parameter. No test-list file changed for this reference.

Configure optional nvMMH tactic pruning and scheduler guidance for CuTe DSL
BF16, FP8, NVFP4 and MXFP8 runners. Separate search policies and profiling
timers in cache identity, prefer CUPTI timing and fall back to CUDA events.
Expose the policy through LLM args and layerwise YAML configuration.

Use main's separate Rubin BF16 runners, direct split-K and public DSL gates.
Preserve current dispatch, telemetry policies and validated baseline tactic
families. Use in-process profiling.

Validation after decoupling: 61 checks passed on Hecate SM107 (39 autotuner,
12 focused NVMMH, 10 Rubin kernel tests). Golden manifest regenerated and
touched-file pre-commit passed. CUPTI is unavailable in this setup; CUDA-event
fallback is verified. Reused recent native binaries, not an exact-tip rebuild.

Signed-off-by: peaceh <103117813+peaceh-nv@users.noreply.github.com>
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  • docs/source/torch/adding_custom_kernels.md
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  • tensorrt_llm/_torch/custom_ops/cutedsl_matmul_heuristics.py
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Walkthrough

The pull request adds process-wide NVMMH configuration, heuristic-based tactic filtering, profiler-aware cache handling, CuTe DSL runner integration, benchmark configuration, and regression coverage for split-K, scheduling, profiling, numerical correctness, and policy ownership.

Changes

NVMMH autotuner integration

Layer / File(s) Summary
Configuration contracts and wiring
docs/source/torch/adding_custom_kernels.md, examples/layer_wise_benchmarks/*, tensorrt_llm/llmapi/*, tensorrt_llm/_torch/pyexecutor/model_engine.py, tensorrt_llm/usage/llm_args_golden_manifest.json
Adds validated NVMMH configuration through Python APIs, LLM API YAML, benchmark YAML, and model-engine initialization.
Autotuner policy, profiling, and cache handling
tensorrt_llm/_torch/autotuner.py
Adds process-wide policy updates, tactic-search cache identities, profiler timing selection, CUPTI failure detection, and CUDA-event fallback.
NVMMH heuristic adapter and tactic filtering
tensorrt_llm/_torch/custom_ops/cutedsl_matmul_heuristics.py
Adds split-K extraction and querying, FP8 and BF16 tactic matching, scheduler-field handling, and fallback preservation.
CuTe DSL runner and kernel integration
tensorrt_llm/_torch/custom_ops/cute_dsl_custom_ops.py, tensorrt_llm/_torch/custom_ops/torch_custom_ops.py, tensorrt_llm/_torch/cute_dsl_kernels/*, tensorrt_llm/_torch/locality_domain/autotune.py, tensorrt_llm/_torch/moe/fused_moe/fused_moe_cute_dsl.py
Migrates runners to NVMMH-aware interfaces and propagates raster, swizzle, TMA-store, and split-K options through caches and kernels.
Regression and architecture-specific validation
tests/unittest/_torch/misc/test_autotuner.py, tests/unittest/_torch/thop/parallel/test_fp8_block_scale_gemm.py, tests/unittest/api_stability/references/llm.yaml
Adds coverage for tactic validity, pruning, performance, numerical equivalence, split-K behavior, replay, and the new API parameter.

Priority: ➖ Normal

Estimated code review effort: 5 (Critical) | ~90 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant PyTorchModelEngine
  participant AutoTuner
  participant CuteDSLTunableRunner
  participant nvMatmulHeuristics
  PyTorchModelEngine->>AutoTuner: configure NVMMH policy
  AutoTuner->>CuteDSLTunableRunner: provide normalized policy
  CuteDSLTunableRunner->>nvMatmulHeuristics: rank validated tactics
  nvMatmulHeuristics-->>CuteDSLTunableRunner: return filtered tactics
  CuteDSLTunableRunner-->>AutoTuner: profile selected tactics
Loading

Suggested reviewers: juney-nvidia

Merge Risk: ⚪ Minimal · up to d9b28

The previously identified policy ownership, split-K admission, and swizzle-test gaps are addressed, so the change is ready for normal merge checks.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 79.82% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 114 functions across 12 files. (2 skipped… Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (4 passed)
Check name Status Explanation
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Title check ✅ Passed The title follows the required ticket and type format and clearly describes the main change: pruning CuTe DSL GEMM autotuner tactics with nvMatmulHeuristics.
Description check ✅ Passed The description explains the motivation, implementation, configuration, supported runners, profiling behavior, tests, workload, and performance results. It provides sufficient coverage for the reposit…
Full details: Docstring Coverage

Explanation

Docstring coverage is 79.82% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 114 functions across 12 files. (2 skipped: 1 unsupported, 1 too large.)

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Actionable comments posted: 3

🧹 Nitpick comments (1)
tensorrt_llm/_torch/pyexecutor/model_engine.py (1)

301-314: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Add test coverage for the autotuner_nvmmh_config wiring.

The tests contain no call to _configure_autotuner_nvmmh and no model-engine construction with a non-default autotuner_nvmmh_config. Existing NVMMH tests call AutoTuner.configure_nvmmh(...) directly, so they do not detect regressions in propagating enabled=True, fields, or max_tactics.

Add a focused test in tests/unittest/_torch/misc/test_autotuner.py that calls _configure_autotuner_nvmmh with a non-default TorchLlmArgs.autotuner_nvmmh_config and asserts the installed AutoTuner.get().nvmmh_config fields.

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In `@tensorrt_llm/_torch/pyexecutor/model_engine.py` around lines 301 - 314, Add
focused coverage for _configure_autotuner_nvmmh in the autotuner tests:
construct TorchLlmArgs with a non-default autotuner_nvmmh_config, invoke the
helper, and assert AutoTuner.get().nvmmh_config has enabled=True plus the
configured fields and max_tactics values.
🤖 Prompt for all review comments with AI agents
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Inline comments:
In `@tensorrt_llm/_torch/custom_ops/cute_dsl_custom_ops.py`:
- Around line 13365-13369: Update the unmatched-swap re-addition in the
surrounding tactic selection logic to iterate over candidate_tactics rather than
fallback_tactics, preserving the split-K eligibility filtering applied earlier
by is_sm107_nvmmh_split_k_eligible while retaining the existing signature and
unmatched-swaps checks.

In `@tensorrt_llm/_torch/pyexecutor/model_engine.py`:
- Around line 301-314: Update _configure_autotuner_nvmmh to preserve the
process-wide NVMMH policy across repeated engine construction: reuse the already
installed AutoTuner policy when equivalent, or reject any differing
autotuner_nvmmh_config instead of replacing it. Keep the initial policy
installation behavior unchanged for the first engine.

In `@tests/unittest/_torch/thop/parallel/test_fp8_block_scale_gemm.py`:
- Around line 801-811: Update the swizzle-variant test around
get_valid_tactics() and _apply_nvmmh_scheduler() to use deterministic NVMMH
swizzle results, keeping baseline tactic membership validation separate from
full returned-tuple assertions. Verify static mode includes the expected swizzle
sizes, while clc_dynamic returns only swizzle_size=1, and assert the complete
tuple shape rather than tactic[:-1].

---

Nitpick comments:
In `@tensorrt_llm/_torch/pyexecutor/model_engine.py`:
- Around line 301-314: Add focused coverage for _configure_autotuner_nvmmh in
the autotuner tests: construct TorchLlmArgs with a non-default
autotuner_nvmmh_config, invoke the helper, and assert
AutoTuner.get().nvmmh_config has enabled=True plus the configured fields and
max_tactics values.

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📒 Files selected for processing (19)
  • docs/source/torch/adding_custom_kernels.md
  • examples/layer_wise_benchmarks/README.md
  • examples/layer_wise_benchmarks/config_ctx.yaml
  • examples/layer_wise_benchmarks/config_gen.yaml
  • examples/layer_wise_benchmarks/run.py
  • tensorrt_llm/_torch/autotuner.py
  • tensorrt_llm/_torch/custom_ops/cute_dsl_custom_ops.py
  • tensorrt_llm/_torch/custom_ops/cutedsl_matmul_heuristics.py
  • tensorrt_llm/_torch/custom_ops/torch_custom_ops.py
  • tensorrt_llm/_torch/cute_dsl_kernels/rubin/dense_bf16_gemm_persistent.py
  • tensorrt_llm/_torch/locality_domain/autotune.py
  • tensorrt_llm/_torch/moe/fused_moe/fused_moe_cute_dsl.py
  • tensorrt_llm/_torch/pyexecutor/model_engine.py
  • tensorrt_llm/llmapi/__init__.py
  • tensorrt_llm/llmapi/llm_args.py
  • tensorrt_llm/usage/llm_args_golden_manifest.json
  • tests/unittest/_torch/misc/test_autotuner.py
  • tests/unittest/_torch/thop/parallel/test_fp8_block_scale_gemm.py
  • tests/unittest/api_stability/references/llm.yaml

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Comment thread tensorrt_llm/_torch/custom_ops/cute_dsl_custom_ops.py
Comment thread tensorrt_llm/_torch/pyexecutor/model_engine.py Outdated
Comment thread tests/unittest/_torch/thop/parallel/test_fp8_block_scale_gemm.py Outdated
Keep split-K admission filtering when restoring unmatched swap orientations.
Pin the process-wide NVMMH configuration while engines remain active, reject
conflicting updates atomically, and release ownership during cleanup or GC.
Equivalent policies reuse the installed snapshot.

Cover engine configuration wiring and lifecycle, unmatched-swap admission,
and deterministic complete swizzle annotations with regression tests. Add
docstrings for changed helpers and correct the documented Blackwell BF16
field support.

Validation: 43 autotuner tests and 2 Rubin MXFP8 scheduler tests passed on
Hecate SM107. The four policy/admission cases passed again after the final
identity-preservation adjustment. The LLM args golden manifest is unchanged.

Signed-off-by: peaceh <103117813+peaceh-nv@users.noreply.github.com>
@peaceh-nv
peaceh-nv force-pushed the user/peaceh/nvmmh-integration-squashed branch from 6bf37b6 to d9b28e8 Compare September 17, 2026 07:40
@peaceh-nv peaceh-nv added the api-compatible Accepted LLM API contract change that is backwards-compatible label Sep 17, 2026
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