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@ixlmar ixlmar commented Nov 11, 2025

Description

  • Extends unit tests to check that there are no device syncs in sample_async.

  • Opportunistic refactor of TestBatchedSampling.test_samples, as suggested in [TRTLLM-8377][test] unit tests for TorchSampler batched sampling #9012 (review). Consider reviewing using something like git diff --color=always --color-moved=plain --color-moved-ws=allow-indentation-change HEAD^, since the PR actually only changes ~300 LoC.

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PR improves existing tests.

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Summary by CodeRabbit

  • Tests
    • Enhanced test infrastructure with improved warmup handling and CUDA synchronization diagnostics to strengthen test reliability and error detection.

@ixlmar ixlmar requested review from Funatiq and dcampora November 11, 2025 16:56
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ixlmar commented Nov 11, 2025

/bot run

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📝 Walkthrough

Walkthrough

The pull request introduces test infrastructure enhancements for controlled warmup behavior and CUDA synchronization validation. It refactors test harnesses across sampling tests to use a new parametrized warmup runner, adds data structures for sampling parameter and result tracking, introduces backend instrumentation for FlashInfer testing, and improves timeout diagnostics using faulthandler.

Changes

Cohort / File(s) Summary
Sampling test infrastructure
tests/unittest/_torch/sampler/test_torch_sampler.py
Adds _run_test_with_warmup helper and UutProvider protocol for executing tests with controlled warmup. Introduces data structures (_TorchUtilsSamplingParams, _MockSamplingLogEntry, UutResult) to track sampling inputs and results. Implements _instrument_sampling_backend and _inject_batching_check for FlashInfer instrumentation. Reworks existing tests (e.g., test_select_generated_logits, test_probs, test_samples, test_unbatch_sampling_results) to use new warmup pattern. Expands typing imports.
Test utilities
tests/unittest/utils/util.py
Adds faulthandler import. Changes DeviceSleepCtl to use @dataclass(kw_only=True). Enhances assert_no_cuda_sync with faulthandler timeout tracing via dump_traceback_later, increased sleep duration (2 * sync_timeout_s), and temporary CUDA sync debug mode set to "error". Updates function signatures with explicit line breaks and trailing commas.

Sequence Diagram(s)

sequenceDiagram
    participant Test as Test Runner
    participant WarmupRunner as _run_test_with_warmup
    participant UUT as Unit Under Test
    participant Backend as Sampling Backend
    participant Checker as Sync/Batch Checker

    Test->>WarmupRunner: Provide UUT, params, is_warmup flag
    WarmupRunner->>WarmupRunner: Warmup phase (if enabled)
    WarmupRunner->>Checker: Setup interception
    Note over Checker: Inject batching/sync checks
    WarmupRunner->>UUT: Execute with warmup context
    UUT->>Backend: Call sampling
    Backend->>Checker: Intercept sampling call
    Checker->>Checker: Log sampling inputs<br/>(top_k, top_p, temp, probs)
    Checker->>Backend: Validate propagation
    Backend-->>UUT: Return samples
    UUT-->>WarmupRunner: Return result
    WarmupRunner->>Checker: Collect logged inputs
    WarmupRunner-->>Test: Return wrapped result
Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~50 minutes

  • tests/unittest/_torch/sampler/test_torch_sampler.py: Multiple new test data structures, instrumentation logic for FlashInfer backend interception, widespread refactoring of existing test invocations to use new warmup pattern, and per-call validation logic requiring careful verification of sampling parameter propagation.
  • tests/unittest/utils/util.py: Enhanced assert_no_cuda_sync with faulthandler integration and CUDA debug mode management requires careful review to ensure correct timeout tracing behavior and context restoration.
  • Cross-file integration between sampling tests and updated utilities needs verification that warmup context and sync checking work as intended.

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)
Check name Status Explanation Resolution
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✅ Passed checks (2 passed)
Check name Status Explanation
Title check ✅ Passed The title clearly summarizes the main change: extending tests to ensure sampling is async, directly matching the PR's core objective.
Description check ✅ Passed The description covers the primary objective (ensuring no device syncs in sample_async) and mentions test coverage, though it lacks detailed explanation of implementation approach and changes.
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Actionable comments posted: 1

🧹 Nitpick comments (1)
tests/unittest/_torch/sampler/test_torch_sampler.py (1)

362-402: Consider documenting the memory allocation strategy.

The _run_test_with_warmup function allocates large buffers (default 4GB) during warmup to prevent PyTorch's caching allocator from triggering device synchronization. While this is a sound strategy, consider adding a note in the docstring about when users might need to adjust warmup_sizes_bytes for GPUs with limited memory.

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📥 Commits

Reviewing files that changed from the base of the PR and between ec9cf71 and b389bfa.

📒 Files selected for processing (2)
  • tests/unittest/_torch/sampler/test_torch_sampler.py (16 hunks)
  • tests/unittest/utils/util.py (4 hunks)
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Files:

  • tests/unittest/_torch/sampler/test_torch_sampler.py
  • tests/unittest/utils/util.py
**/*.{cpp,cxx,cc,h,hpp,hh,hxx,cu,cuh,py}

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Files:

  • tests/unittest/_torch/sampler/test_torch_sampler.py
  • tests/unittest/utils/util.py
🧬 Code graph analysis (1)
tests/unittest/_torch/sampler/test_torch_sampler.py (4)
tests/unittest/utils/util.py (1)
  • assert_no_cuda_sync (503-537)
tensorrt_llm/_torch/pyexecutor/sampler.py (3)
  • get_generator (660-674)
  • _request_get_sampling_params (252-262)
  • _unbatch_sampling_results (1370-1412)
tensorrt_llm/_torch/pyexecutor/scheduler.py (1)
  • ScheduledRequests (20-41)
tensorrt_llm/_torch/pyexecutor/sampling_utils_flashinfer.py (4)
  • sample_grouped_strategies (555-576)
  • FlashInferGroupedStrategySampler (515-576)
  • _StrategyImpls (46-512)
  • StrategyImpl (47-169)
🪛 Ruff (0.14.4)
tests/unittest/_torch/sampler/test_torch_sampler.py

423-423: Unused function argument: is_warmup

(ARG001)


1278-1278: zip() without an explicit strict= parameter

Add explicit value for parameter strict=

(B905)


2173-2173: Unused function argument: is_warmup

(ARG001)

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  • GitHub Check: Pre-commit Check
🔇 Additional comments (11)
tests/unittest/utils/util.py (4)

15-15: LGTM!

The faulthandler import is appropriate for the enhanced timeout diagnostics in assert_no_cuda_sync.


489-494: LGTM!

The signature formatting with trailing commas and explicit keyword-only parameters improves readability and maintainability.


503-534: LGTM!

The enhanced CUDA synchronization detection mechanism combines Python's faulthandler with PyTorch's sync debug mode, providing comprehensive coverage for both general and PyTorch-specific synchronization issues. The 2x timeout margin ensures the device sleep outlasts legitimate async operations.


476-476: No breaking changes detected—the change is safe.

All instantiations of DeviceSleepCtl use zero arguments (DeviceSleepCtl()), which is compatible with kw_only=True because the single field _cancellation_requested has a default value. No code attempts to use positional arguments.

tests/unittest/_torch/sampler/test_torch_sampler.py (7)

15-30: LGTM!

The expanded imports support the new test infrastructure with protocols, context managers, and comprehensive type annotations.


423-559: LGTM!

The refactoring to use the new _run_test_with_warmup pattern correctly integrates the warmup and sync checking infrastructure. The unused is_warmup parameter flagged by static analysis is required by the UutProvider protocol and can be safely ignored.


1114-1148: LGTM!

The integration of synchronization checking into the _sample method is well-designed. Checking only the first iteration prevents queue saturation issues while still validating async behavior.


1240-1400: LGTM!

The refactoring of test_probs correctly integrates the warmup infrastructure. Using separate request objects for warmup prevents state pollution from attached probability outputs.


1402-1844: LGTM!

The new helper methods provide comprehensive test instrumentation. The backend patching strategy and statistical validation using G-tests are appropriate for validating sampling correctness.


1932-2073: LGTM!

The refactoring of test_samples correctly integrates the warmup infrastructure while maintaining comprehensive sampling validation through statistical tests.


2172-2266: LGTM!

The refactoring of test_unbatch_sampling_results correctly integrates the warmup and sync checking infrastructure. The unused is_warmup parameter flagged by static analysis is required by the UutProvider protocol.

@ixlmar ixlmar marked this pull request as draft November 11, 2025 17:04
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PR_Github #24206 [ run ] triggered by Bot. Commit: b389bfa

@ixlmar ixlmar force-pushed the feat/async-sampling-tests branch from b389bfa to 31880b6 Compare November 11, 2025 17:12
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ixlmar commented Nov 11, 2025

/bot run

@ixlmar ixlmar marked this pull request as ready for review November 11, 2025 17:13
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PR_Github #24207 [ run ] triggered by Bot. Commit: 31880b6

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PR_Github #24206 [ run ] completed with state ABORTED. Commit: b389bfa
LLM/main/L0_MergeRequest_PR #18253 (Blue Ocean) completed with status: ABORTED

Signed-off-by: ixlmar <206748156+ixlmar@users.noreply.github.com>
@ixlmar ixlmar force-pushed the feat/async-sampling-tests branch from 31880b6 to aa376d6 Compare November 11, 2025 17:40
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ixlmar commented Nov 11, 2025

/bot run

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PR_Github #24209 [ run ] triggered by Bot. Commit: aa376d6

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PR_Github #24207 [ run ] completed with state ABORTED. Commit: 31880b6
LLM/main/L0_MergeRequest_PR #18254 (Blue Ocean) completed with status: ABORTED

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PR_Github #24209 [ run ] completed with state SUCCESS. Commit: aa376d6
/LLM/main/L0_MergeRequest_PR pipeline #18256 completed with status: 'FAILURE'

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ixlmar commented Nov 12, 2025

/bot run --disable-fail-fast

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PR_Github #24281 [ run ] triggered by Bot. Commit: aa376d6

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PR_Github #24281 [ run ] completed with state SUCCESS. Commit: aa376d6
/LLM/main/L0_MergeRequest_PR pipeline #18317 completed with status: 'SUCCESS'

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LGTM. Thanks for breaking down the tests and adding comments.

@ixlmar ixlmar merged commit 264d38e into NVIDIA:main Nov 12, 2025
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@ixlmar ixlmar deleted the feat/async-sampling-tests branch November 12, 2025 14:27
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