dotnet / dotnet/perf-autofiling-issues

[Perf] Linux/x64: 3 Regressions on 1/21/2026 10:32:30 AM +00:00

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arch-x64 branch-refs/heads/main kind-micro os-linux perf-regression runtime-coreclr untriaged
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Description

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | TigerUbuntu
Baseline | [0b3ba66a27a82e8a039d32a8d9aa3bd94a4f3e4c](https://github.com/dotnet/runtime/commit/0b3ba66a27a82e8a039d32a8d9aa3bd94a4f3e4c)
Compare | [b1d2e4aa8af89cfa795015e30ef70d24ec92f67f](https://github.com/dotnet/runtime/commit/b1d2e4aa8af89cfa795015e30ef70d24ec92f67f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/0b3ba66a27a82e8a039d32a8d9aa3bd94a4f3e4c...b1d2e4aa8af89cfa795015e30ef70d24ec92f67f)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Memory.ReadOnlySpan

Benchmark | Baseline | Test | Test/Base | Test Quality | Edge Detector | Baseline IR | Compare IR | IR Ratio
-- | -- | -- | -- | -- | -- | -- | -- | --
|

  • [IndexOfString - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 13.93 ns | 15.21 ns | 1.09 | 0.14 | False | | |
|
  • [IndexOfString - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 13.91 ns | 15.30 ns | 1.10 | 0.14 | False | | |

![graph]()
![graph]()
[Test Report]()

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

```cmd
git clone https://github.com/dotnet/performance.git
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Memory.ReadOnlySpan*'
```

### System.Memory.ReadOnlySpan.IndexOfString(input: "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAXAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", value: "X", comparisonType: Ordinal)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.ReadOnlySpan.IndexOfString(input: "だだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだxだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだだ", value: "x", comparisonType: Ordinal)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

[Profiling workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-dotnet-runtime.md)
[Benchmarking workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/benchmarking-workflow-dotnet-runtime.md)

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | TigerUbuntu
Baseline | [0b3ba66a27a82e8a039d32a8d9aa3bd94a4f3e4c](https://github.com/dotnet/runtime/commit/0b3ba66a27a82e8a039d32a8d9aa3bd94a4f3e4c)
Compare | [b1d2e4aa8af89cfa795015e30ef70d24ec92f67f](https://github.com/dotnet/runtime/commit/b1d2e4aa8af89cfa795015e30ef70d24ec92f67f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/0b3ba66a27a82e8a039d32a8d9aa3bd94a4f3e4c...b1d2e4aa8af89cfa795015e30ef70d24ec92f67f)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Text.Json.Tests.Perf_Base64

Benchmark | Baseline | Test | Test/Base | Test Quality | Edge Detector | Baseline IR | Compare IR | IR Ratio
-- | -- | -- | -- | -- | -- | -- | -- | --
|

  • [WriteByteArrayAsBase64_NoEscaping - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 99.59 ns | 109.94 ns | 1.10 | 0.37 | False | | |

![graph]()
[Test Report]()

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

```cmd
git clone https://github.com/dotnet/performance.git
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.Json.Tests.Perf_Base64*'
```

### System.Text.Json.Tests.Perf_Base64.WriteByteArrayAsBase64_NoEscaping(NumberOfBytes: 1000)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

[Profiling workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-dotnet-runtime.md)
[Benchmarking workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/benchmarking-workflow-dotnet-runtime.md)

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