[Perf] Windows/x64: 1 Regression on 2/14/2026 12:49:01 AM +00:00

[performanceautofiler]

Run Information

Name	Value
Architecture	x64
OS	Windows 10.0.22631
Queue	ViperWindows
Baseline	52f93b5e2c17ecef33c9d1db82a613fd4c6df6ca
Compare	1be81201324528909e18b8c08511d24e277e70cc
Diff	Diff
Configs	CompilationMode:tiered, RunKind:micro

Regressions in System.Net.Primitives.Tests.CredentialCacheTests

Benchmark	Baseline	Test	Test/Base	Test Quality	Edge Detector	Baseline IR	Compare IR	IR Ratio
GetCredential_Uri - Duration of single invocation 📝 - Benchmark Source ADX - Test Multi Config Graph	309.13 ns	417.94 ns	1.35	0.30	False

Test Report

Repro

General Docs link: https://github.com/dotnet/performance/blob/main/docs/benchmarking-workflow-dotnet-runtime.md

git clone https://github.com/dotnet/performance.git
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Net.Primitives.Tests.CredentialCacheTests*'

Details

System.Net.Primitives.Tests.CredentialCacheTests.GetCredential_Uri(uriString: "http://name5", uriCount: 10)

ETL Files

Histogram

JIT Disasms

Docs

Profiling workflow for dotnet/runtime repository
Benchmarking workflow for dotnet/runtime repository

[LoopedBard3]

🔍 Automated Triage Analysis

Summary: Clear regression in CredentialCache.GetCredential_Uri (+35.2%, z=7.06) attributed to commit 12f45a0 (Uri parsing fix). The change to Uri constructor logic introduced overhead in credential cache lookups. Historical data shows stable baseline with 308 runs before a definitive step change at the regression point.

Finding Confidence: 4/5 (analysis accuracy)
Regression Confidence: 4/5 (likelihood of true regression)

Likely Cause: 12f45a037d3a

📊 Full Analysis (click to expand)

Issue Overview

• Issue: #68863 - [Perf] Windows/x64: 1 Regression on 2/14/2026 12:49:01 AM +00:00
• Date: 2026-02-14 | Queue: Windows.11.Amd64.Viper.Perf | OS/Arch: Windows 10.0.22631/x64
• Commits: 52f93b5e2c17 → 1be812013245 (18 commits)
• Labels: untriaged, perf-regression, os-windows, arch-x64, branch-refs/heads/main, runtime-coreclr, kind-micro
• Historical Data: Available (308 prior runs, excellent quality)

Test Analysis

Test Name	Baseline	Compare	Δ%	μ	σ	n	z	Thresh%	Noise?	Assessment
GetCredential_Uri(uriString: "http://name5", uriCount: 10)	309.13 ns	417.94 ns	+35.2%	320.89 ns	13.74 ns	308	7.06	8.56%	N	Step change, stable baseline

Legend: μ=mean, σ=stddev, n=runs, z=z-score, Thresh%=adaptive threshold

Finding Confidence: 4/5 - Strong historical data with 308 prior runs, low variance (CV=4.28%), clear bifurcation at regression point. No verification via RunWithBuildAtHash performed, but data quality is excellent.

Confirmed Regressions

System.Net.Primitives.Tests.CredentialCacheTests.GetCredential_Uri(uriString: "http://name5", uriCount: 10) (+35.2%)

• Delta: 309.13 ns → 417.94 ns (+35.2%)
• Historical Context: μ=320.89 ns (σ=13.74 ns, n=308); z-score=7.06; adaptive threshold=8.56%
• Assessment: Clear step change - performance jumped from ~305-335ns range to ~418-444ns range immediately at regression commit. The z-score of 7.06 indicates the compare value is 7 standard deviations above historical mean. Low coefficient of variation (4.28%) confirms stable baseline, making this a definitive regression.
• Finding Confidence: 4/5 - Excellent historical data (308 runs), stable baseline, clear bifurcation. Not upgraded to 5/5 because no verification via RunWithBuildAtHash was performed.
• Regression Confidence: 4/5 - Strong signal (z=7.06, delta far exceeds threshold), direct code path connection to Uri parsing, focused commit range (18 commits). Not upgraded to 5/5 due to lack of direct bisection verification.
• Likely Cause: 12f45a037d3a - "Fix parsing inconsistencies between Uri ctors and TryCreate factories (Fix parsing inconsistencies between Uri ctors and TryCreate factories #123932)"
  • Affected Areas: System.Private.Uri - Uri parsing and creation logic
  • Rationale: This commit directly modifies Uri constructor and factory method behavior in System.Private.Uri/src/System/Uri.cs and UriExt.cs. The CredentialCache.GetCredential method performs Uri lookups and comparisons, which would be affected by changes to Uri parsing/creation paths. The commit refactored how Uri objects are constructed and validated, moving DebugSetLeftCtor() calls earlier in the construction pipeline, which could introduce additional overhead in Uri creation/comparison operations. The timing aligns perfectly - committed 2026-02-13T21:26:35, within the 18-commit range leading to the regression timestamp.
  • Candidates Considered:
    • 12f45a037d3a - "Fix parsing inconsistencies between Uri ctors and TryCreate factories" - Most likely: Direct Uri code path, affects credential lookup operations
    • 60810191b26c - "Fix ConnectAsync sending stale ReceiveAsync buffer via ConnectEx" - Less likely: Socket-level change, not directly related to credential cache lookups
    • c1cb90983ae7 - "cDAC loader GetModuleData - remove unneeded transient flags" - Unlikely: Debugging/diagnostics infrastructure, timestamp matches regression but no functional connection
• Verification Status: Not verified - Historical data provides strong evidence, but RunWithBuildAtHash confirmation would increase confidence to 5/5.

Open Questions

• Verification Needed: While historical data strongly indicates a regression, verification via RunWithBuildAtHash on commit 12f45a0 vs baseline would confirm attribution and eliminate any doubt about environmental factors.
• Root Cause Mechanism: The Uri parsing changes appear to have introduced overhead in either Uri construction, comparison, or lookup operations. Detailed profiling would identify whether the overhead is in:
  • Uri object creation (constructor path changes)
  • Uri comparison/equality operations used by CredentialCache
  • Uri validation/parsing during lookup operations
• Mitigation Options: If confirmed, investigate whether the parsing correctness fix can be optimized to reduce overhead, or if there are opportunities to cache/optimize Uri operations in CredentialCache.

Recommended Actions

1. Verification: Run bisection using RunWithBuildAtHash on commits 52f93b5e2c17...1be812013245 to confirm commit 12f45a0 as the exact culprit and measure the precise performance impact at that commit.
2. Profiling: If verified, collect detailed performance traces with hardware counters (instructions retired, branch mispredictions, cache misses) to understand the specific overhead introduced by the Uri parsing changes.
3. Source review: Manual code review of commit 12f45a0 focusing on:
   • The impact of moving DebugSetLeftCtor() earlier in Uri construction
   • Any new validation or parsing steps added to Uri ctors/factories
   • How CredentialCache.GetCredential uses Uri objects for lookups
   • Potential optimization opportunities in the new code paths
4. Engage with author: Contact MihaZupan to discuss the performance impact and explore optimization options that preserve the correctness fix while reducing overhead.

Structured Summary (JSON)

{
  "schemaVersion": "perf-triage-v1",
  "issue": 68863,
  "baselineCommit": "52f93b5e2c17ecef33c9d1db82a613fd4c6df6ca",
  "compareCommit": "1be81201324528909e18b8c08511d24e277e70cc",
  "commitRangeSize": 18,
  "historicalContext": {
    "runsExamined": 308,
    "missing": false,
    "notes": "Excellent data quality with 308 historical runs before regression. Historical measurements very stable (CV=4.28%). Clear bifurcation in performance at regression timestamp."
  },
  "regressions": [
    {
      "test": "System.Net.Primitives.Tests.CredentialCacheTests.GetCredential_Uri(uriString: \"http://name5\", uriCount: 10)",
      "baseline": 309.13,
      "compare": 417.94,
      "percentDelta": 35.2,
      "histMean": 320.89,
      "histStdDev": 13.74,
      "zScore": 7.06,
      "isNoise": false,
      "likelyCommit": "12f45a037d3a13e4b78c45ffe736ca96f93e58e3",
      "findingConfidence": 4,
      "findingConfidenceRationale": "Excellent historical data (308 runs), low variance (CV=4.28%), clear bifurcation at regression point. Not upgraded to 5/5 because no verification via RunWithBuildAtHash was performed.",
      "regressionConfidence": 4,
      "regressionConfidenceRationale": "Strong signal (z=7.06, delta +35.2% far exceeds adaptive threshold of 8.56%), direct code path connection to Uri parsing which affects credential cache lookups, focused commit range (18 commits). Not upgraded to 5/5 due to lack of direct bisection verification.",
      "verified": false,
      "bisected": false,
      "bisectionRange": null
    }
  ],
  "nextActions": [
    "Verify regression with RunWithBuildAtHash on suspected commit 12f45a037d3a vs baseline 52f93b5e2c17",
    "Bisect commit range to confirm exact culprit commit",
    "Profile with hardware counters to understand Uri parsing overhead mechanism",
    "Manual code review of Uri parsing changes focusing on CredentialCache interaction",
    "Engage with commit author MihaZupan to discuss optimization opportunities"
  ],
  "generationNotes": "Strong regression detected with excellent historical data. Attribution based on code path analysis and timing correlation. Verification recommended to achieve highest confidence level."
}

---

Generated by PerfTriageAgent on 2026-02-17 10:02 UTC

[DrewScoggins]

Related to #123932