fix(frost): drain final MoE scheduler broadcast - #813
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Included review availability: Your plan provides up to 12 included reviews per hour; 8 remain after this review. 📝 WalkthroughWalkthroughThe MoE grouped matmul schedulers now record the final invalid broadcast state and drain multi-CTA acknowledgements before scheduler-warp exit. Obsolete scheduler code-generation helpers and tests are removed. The routed output comments now describe a flat ChangesMoE scheduler broadcast drain
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to This localized change drains the final grouped-MoE scheduler broadcast while preserving existing API behavior; no actionable merge-blocking risk remains after normal checks and review. Sequence Diagram(s)sequenceDiagram
participant SchedulerLeaderCTA
participant SchedulerWarps
participant ClusterAcknowledgements
SchedulerLeaderCTA->>SchedulerWarps: Record final broadcast stage and parity
SchedulerWarps->>ClusterAcknowledgements: Acknowledge final invalid broadcast
SchedulerLeaderCTA->>ClusterAcknowledgements: Wait for multi-CTA acknowledgements
SchedulerLeaderCTA->>SchedulerWarps: Exit after acknowledgement drain
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Description checkExplanation The description includes all required sections and provides a clear summary, rationale, compatibility impact, related-issue status, and detailed testing results. It also explains the Projects-field limitation while confirming the milestone is set. ✨ Finishing Touches 💡 1🛠️ Fix failing CI checks 💡
🧪 Generate unit tests (beta)
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Each persistent cluster emits one invalid scheduler record before its scheduler warp exits. The final ring slot is never reused, so the leader previously could leave while peer CTAs still acknowledged its distributed shared-memory barrier. Retain the exact broadcast stage and completion parity, then keep the leader alive until every scheduler warp acknowledges the final record. Compile the snapshot and wait out for singleton clusters, which have no remote DSM lifetime. Cover plain and block-scaled MoE templates across 1x1, 1x2, and 2x1 scheduler geometries.
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Inline comments:
In `@test/python/gemm/frost/test_moe_grouped_matmul_fwd.py`:
- Around line 218-223: Add the appropriate registered L0–L4 test-level marker to
each specified test: test_moe_scheduler_codegen_drains_final_cluster_broadcast
and test_moe_tma_store_uses_rank2_output_descriptor in
test/python/gemm/frost/test_moe_grouped_matmul_fwd.py (lines 218-223 and
585-602), plus test_moe_block_scale_tma_store_uses_rank2_output_descriptor and
test_moe_block_scale_scheduler_codegen_drains_final_cluster_broadcast in
test/python/gemm/frost/test_moe_grouped_block_scale_matmul_fwd.py (lines 263-279
and 290-295).
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python/cudnn/gemm/frost/kernel_templates/sm100_moe_grouped_block_scale_matmul_fwd.pypython/cudnn/gemm/frost/kernel_templates/sm100_moe_grouped_matmul_fwd.pytest/python/gemm/frost/gemm_test_utils.pytest/python/gemm/frost/test_moe_grouped_block_scale_matmul_fwd.pytest/python/gemm/frost/test_moe_grouped_matmul_fwd.py
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Before submitting
pre-commit runand committed any formatting changes.cat-*, one or moremod-*, and oneorig-*(see label list).Affected area
FE OSS kernels or CuTeDSL
Summary
This is a correctness/lifetime fix with no public API or model-performance claim.
Why
Normal ring reuse waits for acknowledgements before a stage is reused. The final invalid scheduler record exits the loop instead, so no later reuse keeps the leader CTA and its distributed shared-memory barrier alive while peers still acknowledge it.
The fix snapshots the final stage before ring wrap. Each acknowledgement flips the saved pre-wrap empty phase, so
pre-wrap bcast_empty_phase ^ 1is the completed parity waited on by the leader.Related issues
None.
API and compatibility impact
None. This changes only internal scheduler lifetime in the existing FROST grouped-MoE kernels. Singleton clusters compile away the additional state and wait.
Testing
d784e62ae: removed the renderer helper, private schedule constants, regex/exact generated-source assertions, and the two codegen tests. Changed-file pre-commit, Python compilation, and diff checks passed.daf9ba5ba: the complete L0 suites for both affected grouped-MoE families reported 229 passed, 20 skipped. Prior functional smoke covered all six 1x1, 1x2, and 2x1 template/cluster combinations.synccheckreported zero errors before and after;racecheckproduced identical, non-discriminating DSM reports in both versions. Sanitizer silence is supporting evidence rather than proof.No deterministic black-box RED test was found for the DSM lifetime violation. The fix is supported by the broadcast-ring protocol argument and existing fixed-path functional coverage; no timing difference is expected or claimed.
Summary by CodeRabbit
Bug Fixes
Tests