[TRTLLM-15179][test] Add multi-rank test for KVCM v2 host-tier quota sync - #17790
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Included review availability: Your plan includes up to 12 reviews per rolling hour; 11 remain after this review. WalkthroughThe change centralizes multi-rank host-tier quota synchronization in ChangesHost-tier quota synchronization
Integration test waiver
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to This PR adds focused multi-rank regression coverage and a behavior-preserving helper refactor; no actionable merge-blocking risk remains beyond normal checks and review. Sequence Diagram(s)sequenceDiagram
participant Rank0
participant Rank1
participant DistributedMinAllReduce
Rank0->>DistributedMinAllReduce: Submit local host-tier quota
Rank1->>DistributedMinAllReduce: Submit local host-tier quota
DistributedMinAllReduce-->>Rank0: Return fleet minimum
DistributedMinAllReduce-->>Rank1: Return fleet minimum
Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 1🛠️ Fix failing CI checks 💡
🧪 Generate unit tests (beta)
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In `@tensorrt_llm/_torch/pyexecutor/kv_cache_manager_v2.py`:
- Around line 297-299: Update the host quota logic in the KV cache capacity
calculation to normalize each rank’s host bytes into token or block capacity
before the Distributed.allreduce MIN, then convert the fleet-wide minimum back
into each rank’s local byte quota using its local cache cost per token. Mirror
the existing device-quota normalization pattern around the device capacity
logic, and add an MPI test covering heterogeneous PP cache costs.
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tensorrt_llm/_torch/pyexecutor/kv_cache_manager_v2.pytests/unittest/_torch/executor/test_kvv2_host_tier_sizing.py
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…sync The auto host-tier quota is computed from rank-local host state (SC_AVPHYS_PAGES, RLIMIT_MEMLOCK), so co-scheduled ranks can diverge and wedge collectives on non-attention-DP TP; the fix reconciles them with an allreduce(MIN). Only the pure sizing helper was tested. Extract the cross-rank sync into _sync_host_tier_quota and add a 2-rank MpiPoolSession harness test (CPU-only, no GPU) that feeds divergent per-rank auto quotas through the real allreduce(MIN) and asserts every rank converges to the fleet minimum (the most-constrained rank wins), plus a single-rank no-op case. Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
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…failure on main, tracked in https://nvbugs/6630699) Signed-off-by: Brian Nguyen <brnguyen@nvidia.com>
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From what I see, this seems to be related to disagreement between ranks and also, refactor/test-only change. I have an MR which deals with oversubscription of host tier KV cache (specifically by draft KV manager). Kindly have a look when you find some time.
#17850
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Summary
Follow-up from code review of #17380 ("KVCM-V2: sync auto host-tier quota across ranks"). That PR added an
allreduce(MIN)over the auto-computed host cache tier quota so co-located ranks reading differentsysconf(SC_AVPHYS_PAGES)values don't end up with divergent host tiers — divergence made per-rank MAX_UTILIZATION schedulers disagree about which suspended requests can resume, wedging collectives on non-attention-DP TP. The fix merged without a test (kept minimal + urgent). This adds the missing regression coverage (TRTLLM-15179).What changed
KVCacheManagerV2.__init__into a module-level helper_sync_host_tier_quota(host_quota, mapping)inkv_cache_manager_v2.py, next to_compute_auto_host_tier_quota. This makes the sync directly testable — the existingtest_kvv2_host_tier_sizing.pyonly covered the pure sizing helper, not theallreduce.tests/unittest/_torch/executor/test_kvv2_host_tier_sizing.py:test_multi_rank_syncs_to_fleet_min— a real 2-rankMpiPoolSessionharness (CPU-only, no GPU). Each rank simulates a divergent available-memory reading (rank 0 → 220 GiB, rank 1 → 440 GiB), computes its own auto quota via the real helper, and runs the realallreduce(MIN). Asserts the ranks disagreed pre-sync (so the test can't pass vacuously) and that every rank converges to the fleet minimum — the most-constrained rank sets the value.test_single_rank_is_a_noop— covers theworld_size == 1short-circuit (no collective).Test wiring
The test lives under
unittest/_torch/executor, which is collected as a directory glob byl0_cpu.yml(apre_merge,orchestrator: mpi, 0-GPU stage) and the GPU executor stages. The MPI harness runs (not skipped) in the CPU pre-merge stage where MPI is enabled and no GPU is needed.Dev Engineer Review
_sync_host_tier_quotato reduce multi-rank host-tier quotas with a distributedMINall-reduce.KVCacheManagerV2.__init__to use the helper.QA Engineer Review
_sync_host_tier_quota.