[None][feat] Remove padding in Kimi K3 MLA module - #17684
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Included review availability: Your plan provides up to 12 included reviews per hour; 11 remain after this review. WalkthroughKimi MLA now uses ChangesKimi MLA and CuTe DSL MLA
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to This PR removes K3 MLA padding and changes checkpoint loading, but the intended SM107 reduction path remains unavailable and malformed KV-B checkpoints can produce opaque failures without validation. The PR is not merge-ready until these bounded issues are fixed or explicitly accepted by the owner. Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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Actionable comments posted: 1
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Inline comments:
In `@tensorrt_llm/_torch/modules/kimi_k3_mla/kimi_k3_mla_attention.py`:
- Around line 197-209: Update the g_proj Linear construction in KimiMLAAttention
to pass reduce_output=False, preventing reduction of gate values across
tensor-parallel head slices; retain the existing KimiMLARuntime reduction after
the row-parallel o_proj.
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tensorrt_llm/_torch/attention_backend/fmha/cute_dsl_mla.pytensorrt_llm/_torch/models/modeling_kimi_linear.pytensorrt_llm/_torch/modules/kimi_k3_mla/kimi_k3_mla_attention.py
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Actionable comments posted: 1
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Inline comments:
In `@tensorrt_llm/_torch/attention_backend/fmha/cute_dsl_mla.py`:
- Line 273: Update the comment adjacent to the condition using
meta.num_contexts, attn.num_heads, and meta.num_generations to document the
intentional 96-head exception: explain the compacted generation Q slice and the
meta.num_contexts metadata offset, clarify that mixed batches remain disabled
for non-96 head counts, and preserve the existing generation-only check.
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📒 Files selected for processing (3)
tensorrt_llm/_torch/attention_backend/fmha/cute_dsl_mla.pytensorrt_llm/_torch/models/modeling_kimi_linear.pytensorrt_llm/_torch/modules/kimi_k3_mla/kimi_k3_mla_attention.py
🚧 Files skipped from review as they are similar to previous changes (2)
- tensorrt_llm/_torch/modules/kimi_k3_mla/kimi_k3_mla_attention.py
- tensorrt_llm/_torch/models/modeling_kimi_linear.py
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Inline comments:
In
`@tensorrt_llm/_torch/cute_dsl_kernels/blackwell/attention/mla/mla_decode_fp16.py`:
- Around line 2609-2611: Update CuteDslMlaFmha.is_available() to include the
SM107 value returned by get_sm_version() in its supported architecture
allowlist, allowing construction of BlackwellMultiHeadLatentAttentionForwardFP16
on SM107. Add runtime coverage verifying availability and branch execution for
SM107.
Apply the same fix in
`@tensorrt_llm/_torch/cute_dsl_kernels/blackwell/attention/mla/mla_decode_fp8.py`
around lines 2580 - 2582: The same SM107/SM107f availability-gate issue affects
the FP8 branch.
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tensorrt_llm/_torch/attention_backend/fmha/cute_dsl_mla.pytensorrt_llm/_torch/cute_dsl_kernels/blackwell/attention/mla/mla_decode_fp16.pytensorrt_llm/_torch/cute_dsl_kernels/blackwell/attention/mla/mla_decode_fp8.py
🚧 Files skipped from review as they are similar to previous changes (1)
- tensorrt_llm/_torch/attention_backend/fmha/cute_dsl_mla.py
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PR_Github #66256 [ run ] triggered by Bot. Commit: |
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PR_Github #66547 [ run ] triggered by Bot. Commit: |
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PR description issue The auto-generated summary claims: ▎ "Added SM107 and SM107f support for the MLA softmax tensor-memory reduction path." This is stale. Commit ac4f7d2 added the SM107 branch, but commit c9a8229 ("Revert 'add sm107 branch for mla'") reverted it. The final diff contains no SM107-related code at all. The description was generated before the revert and was never updated — please remove/regenerate that line before merging to avoid confusing reviewers and polluting release notes. |
brnguyen2
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Approving — the comments below are optional touch-ups, not blockers.
The loader refactor is the right direction — deleting the hand-rolled pad-then-shard slicing in favor of the owning modules' load_shard removes ~190 lines of duplicated TP policy and the zero-head waste. Remaining concerns, beyond the inline comments:
- TP coverage. The bf16 admission list
{6, 12, 16, 96}covers attention-DP (96) and tp=8/16 (12/6). tp=2 and tp=4 now produce 48/24 per-rank heads that fall back to trtllm-gen — are those head counts known-good on the trtllm-gen generation kernels? Also, TP sizes that don't divide 96 (e.g. 64) now assert at MLA init (num_heads % tp == 0), where the old 128-head padding made them work. If those configs are intentionally dropped, say so in the description. - No tests. The Test Coverage section is empty and there are no test changes for a checkpoint-loader rewrite plus new kernel-admission head counts. Please state which configs were validated end-to-end (attention-DP, tp=8, tp=16; bf16 and FP8 KV cache), and consider a CPU-only unit test that loads a fake KV-B checkpoint at tp>1 and checks
kv_b_proj.weight/k_b_proj_trans/v_b_projagainst the grouped layout — that would lock in the trickiest part of this change. - Ticket. This is a nontrivial feature/perf change; the title carries
[None]— please attach the JIRA ticket. - Description. The mixed-batch exemption for 96 heads is a behavior change worth a sentence in the human-written description, not just the auto-generated summary.
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PR_Github #67313 [ run ] triggered by Bot. Commit: |
Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
This reverts commit ac4f7d2. Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
Signed-off-by: Pengbo Wang <221450789+pengbowang-nv@users.noreply.github.com>
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PR_Github #67336 [ run ] triggered by Bot. Commit: |
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PR_Github #67313 [ run ] completed with state |
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PR_Github #67336 [ run ] completed with state |
8 participants
Dev Engineer Review
KimiMLARuntimeandKimiK3MLAAttentionto requireModelConfig.QA Engineer Review
No test changes.
Description
K3 used to pad mla head from 96 to 128 due to kernel requirement. This PR removed it and use cuteDSL mla decode kernel.
This PR also removed padding and sharding in ckpt loading.
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