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[LLM] add metric observations for vLLM and SGLang - #1068

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@podkidyshev podkidyshev commented Sep 30, 2026 •

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Summary

  • Add metric_observations to vLLM and SGLang for request throughput (requests/s), output-token throughput (tokens/s), TTFT/TPOT (ms), and optional semantic accuracy.
  • Dimensions distinguish produced values: TTFT/TPOT use statistic (mean, median, p99); throughput and accuracy have empty dimensions.

Test Plan

  • Automated CI
  • Manual tests. Run the metric_observations directly on historical vLLM/SGLang runs. The output values correspond to workload artifacts 1:1

Additional Notes

N/A

Signed-off-by: Ivan Podkidyshev <ipodkidyshev@nvidia.com>
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Review in Change Stack →

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📥 Commits

Reviewing files that changed from the base of the PR and between 2869d98 and e653330.

📒 Files selected for processing (10)
  • doc/workloads/sglang.rst
  • doc/workloads/vllm.rst
  • src/cloudai/workloads/common/llm_serving.py
  • src/cloudai/workloads/sglang/sglang.py
  • src/cloudai/workloads/vllm/report_generation_strategy.py
  • tests/workloads/common/test_llm_serving.py
  • tests/workloads/common/test_llm_serving_report.py
  • tests/workloads/sglang/test_job_status_retrieval_strategy.py
  • tests/workloads/sglang/test_report_gen_strategy.py
  • tests/workloads/vllm/test_report_gen_strategy.py

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📝 Walkthrough

Walkthrough

The change adds five serving metrics to the metric catalog and documents them for vLLM and SGLang. Both backends now produce metric observations from benchmark results and optional semantic accuracy through a shared helper. Tests cover observations, filtering, and updated report fixtures.

Changes

LLM Serving Metrics

Layer / File(s) Summary
Serving metric catalog
src/cloudai/metrics.py, doc/workloads/sglang.rst, doc/workloads/vllm.rst
Registers five serving metrics and the statistic dimension. The workload documentation lists metric units, preferred directions, and dimensions.
Backend observations
src/cloudai/workloads/common/llm_serving.py, src/cloudai/workloads/sglang/sglang.py, src/cloudai/workloads/vllm/..., tests/workloads/common/test_llm_serving.py, tests/workloads/common/test_llm_serving_report.py, tests/workloads/sglang/*, tests/workloads/vllm/test_report_gen_strategy.py
Adds throughput fields to backend reports and a shared helper that creates finite metric observations. vLLM and SGLang pass parsed reports and optional accuracy to the helper. Tests cover observations, filtering, and report fixtures.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Merge Risk: 🔵 Low · up to e6533

Out-of-range evaluator output can appear as a valid structured accuracy ratio. The impact is bounded to reported metrics, but the existing concern remains unresolved.

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Title check ✅ Passed The title clearly identifies the main change: adding metric observations for vLLM and SGLang.
Description check ✅ Passed The description summarizes the metrics, dimensions, and testing for the changeset.
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Signed-off-by: Ivan Podkidyshev <ipodkidyshev@nvidia.com>
Signed-off-by: Ivan Podkidyshev <ipodkidyshev@nvidia.com>
@podkidyshev podkidyshev changed the title feat: add metric observations for vLLM and SGLang [LLM] add metric observations for vLLM and SGLang Oct 6, 2026
@podkidyshev podkidyshev self-assigned this Oct 6, 2026
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/build

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@coderabbitai full review

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✅ Action performed

Full review finished.

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Actionable comments posted: 1


  • 🪄 Fix CodeRabbit comments on this PR
🤖 Prompt to fix review comments
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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @src/cloudai/workloads/common/llm_serving.py:
- Around line 252-253: Update the accuracy check before appending a
MetricObservation to accept only finite values within the documented 0–1 range;
omit out-of-range values from structured observations while leaving the existing
scalar accuracy result unchanged.

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📥 Commits

Reviewing files that changed from the base of the PR and between 42724e9 and 2869d98.

📒 Files selected for processing (9)
  • doc/workloads/_llm_serving_metrics.inc
  • doc/workloads/sglang.rst
  • doc/workloads/vllm.rst
  • src/cloudai/metrics.py
  • src/cloudai/workloads/common/llm_serving.py
  • src/cloudai/workloads/sglang/sglang.py
  • src/cloudai/workloads/vllm/report_generation_strategy.py
  • src/cloudai/workloads/vllm/vllm.py
  • tests/workloads/common/test_llm_serving.py

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Comment thread src/cloudai/workloads/common/llm_serving.py
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/build

Signed-off-by: Ivan Podkidyshev <ipodkidyshev@nvidia.com>
Signed-off-by: Ivan Podkidyshev <ipodkidyshev@nvidia.com>
Signed-off-by: Ivan Podkidyshev <ipodkidyshev@nvidia.com>
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/build

@podkidyshev
podkidyshev marked this pull request as ready for review October 6, 2026 15:40
) -> list[cloudai.metrics.MetricObservation]:
"""Use statistics to distinguish latency results; scalar results have no dimensions."""
observations: list[cloudai.metrics.MetricObservation] = []
if accuracy is not None and math.isfinite(accuracy):

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I saw the code rabbit comments. Is it ever possible that it can actually produce NaN/Inf here?

Example: For vLLM: what happens if you have mean([]) --> NaN?

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