[Perf] Linux/x64: 23 Regressions on 1/22/2026 3:57:05 AM +00:00

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#68,008 opened on Jan 27, 2026 6 comments 0 reactions 0 assignees View on GitHub

arch-x64 branch-refs/heads/main kind-micro Look Again os-linux perf-regression RegressionHunter runtime-coreclr

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Forks: 8
PR merge metrics: PR metrics pending

Description

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [b1d2e4aa8af89cfa795015e30ef70d24ec92f67f](https://github.com/dotnet/runtime/commit/b1d2e4aa8af89cfa795015e30ef70d24ec92f67f)
Compare | [a035ab7d42601c2262e6f4d86a9a7d0b93c0c4ec](https://github.com/dotnet/runtime/commit/a035ab7d42601c2262e6f4d86a9a7d0b93c0c4ec)
Diff | [Diff](https://github.com/dotnet/runtime/compare/b1d2e4aa8af89cfa795015e30ef70d24ec92f67f...a035ab7d42601c2262e6f4d86a9a7d0b93c0c4ec)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.Tests.Perf_StreamWriter

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

[WriteCharArray - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 65.82 ms | 73.96 ms | 1.12 | 0.08 | 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.IO.Tests.Perf_StreamWriter*'
```

### System.IO.Tests.Perf_StreamWriter.WriteCharArray(writeLength: 2)

#### 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

### Regressions in System.Tests.Perf_String

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

[ToUpper - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 14.58 ns | 15.64 ns | 1.07 | 0.08 | False | | |
|

[ToLower - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 4.44 ns | 5.63 ns | 1.27 | 0.41 | False | | |
|

[Replace_String - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 6.92 ns | 8.07 ns | 1.17 | 0.15 | False | | |
|

[ToUpper - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 14.30 ns | 15.50 ns | 1.08 | 0.09 | False | | |
|

[ToUpperInvariant - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 0.93 ns | 2.08 ns | 2.23 | 0.54 | False | | |
|

[ToLower - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 14.34 ns | 15.43 ns | 1.08 | 0.08 | False | | |

![graph]()
![graph]()
![graph]()
![graph]()
![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.Tests.Perf_String*'
```

### System.Tests.Perf_String.ToUpper(s: "TeSt")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_String.ToLower(s: "test")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_String.Replace_String(text: "This is a very nice sentence", oldValue: "bad", newValue: "nice")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_String.ToUpper(s: "test")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_String.ToUpperInvariant(s: "TEST")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_String.ToLower(s: "TeSt")

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Threading.Tasks.ValueTaskPerfTest

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

[Copy_PassAsArgumentAndReturn_FromValueTaskSource - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 3.78 ns | 5.21 ns | 1.38 | 0.06 | 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.Threading.Tasks.ValueTaskPerfTest*'
```

### System.Threading.Tasks.ValueTaskPerfTest.Copy_PassAsArgumentAndReturn_FromValueTaskSource

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Runtime.Intrinsics.Tests.Perf_Vector128Of<Byte>

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

[SquareRootBenchmark - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 23.48 ns | 25.14 ns | 1.07 | 0.02 | 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.Runtime.Intrinsics.Tests.Perf_Vector128Of*'
```

### System.Runtime.Intrinsics.Tests.Perf_Vector128Of<Byte>.SquareRootBenchmark

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Text.Json.Document.Tests.Perf_EnumerateArray

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

[EnumerateUsingIndexer - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 110.90 μs | 119.03 μs | 1.07 | 0.03 | 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.Document.Tests.Perf_EnumerateArray*'
```

### System.Text.Json.Document.Tests.Perf_EnumerateArray.EnumerateUsingIndexer(TestCase: Json400KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.IO.Tests.StreamReaderReadToEndTests

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

[ReadToEndAsync - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 61.90 ms | 66.90 ms | 1.08 | 0.01 | False | | |
|

[ReadToEndAsync - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 67.38 ms | 72.44 ms | 1.08 | 0.01 | False | | |
|

[ReadToEndAsync - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 66.70 ms | 71.51 ms | 1.07 | 0.00 | False | | |
|

[ReadToEndAsync - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 65.76 ms | 70.37 ms | 1.07 | 0.01 | False | | |
|

[ReadToEndAsync - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 62.39 ms | 66.71 ms | 1.07 | 0.01 | False | | |

![graph]()
![graph]()
![graph]()
![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.IO.Tests.StreamReaderReadToEndTests*'
```

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 0, 1024])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 1, 8])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 1, 1])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 9, 32])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 129, 1024])

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Text.RegularExpressions.Tests.Perf_Regex_Industry_RustLang_Sherlock

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

[Count - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 889.59 μs | 970.01 μs | 1.09 | 0.02 | 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.RegularExpressions.Tests.Perf_Regex_Industry_RustLang_Sherlock*'
```

### System.Text.RegularExpressions.Tests.Perf_Regex_Industry_RustLang_Sherlock.Count(Pattern: "(?s).*", Options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Text.Tests.Perf_Encoding

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

[GetChars - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 16.16 ns | 17.67 ns | 1.09 | 0.06 | False | | |
|

[GetByteCount - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 4.18 ns | 7.35 ns | 1.76 | 0.06 | 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.Text.Tests.Perf_Encoding*'
```

### System.Text.Tests.Perf_Encoding.GetChars(size: 16, encName: "utf-8")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Tests.Perf_Encoding.GetByteCount(size: 16, encName: "utf-8")

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.IO.Tests.Perf_File

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

[Delete - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 12.09 μs | 17.83 μs | 1.48 | 0.40 | 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.IO.Tests.Perf_File*'
```

### System.IO.Tests.Perf_File.Delete

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Text.Json.Serialization.Tests.WriteJson<LoginViewModel>

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

[SerializeToWriter - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 100.08 ns | 105.61 ns | 1.06 | 0.17 | 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.Serialization.Tests.WriteJson*'
```

### System.Text.Json.Serialization.Tests.WriteJson<LoginViewModel>.SerializeToWriter(Mode: Reflection)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [212076ab3e7e92b1d7701d9ab1a660700ee37b81](https://github.com/dotnet/runtime/commit/212076ab3e7e92b1d7701d9ab1a660700ee37b81)
Compare | [a035ab7d42601c2262e6f4d86a9a7d0b93c0c4ec](https://github.com/dotnet/runtime/commit/a035ab7d42601c2262e6f4d86a9a7d0b93c0c4ec)
Diff | [Diff](https://github.com/dotnet/runtime/compare/212076ab3e7e92b1d7701d9ab1a660700ee37b81...a035ab7d42601c2262e6f4d86a9a7d0b93c0c4ec)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in Devirtualization.EqualityComparer

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

[ValueTupleCompareWrapped - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 0.62 ns | 1.63 ns | 2.63 | 0.33 | 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 'Devirtualization.EqualityComparer*'
```

### Devirtualization.EqualityComparer.ValueTupleCompareWrapped

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in SIMD.RayTracerBench

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

[Bench - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 254.52 ms | 277.70 ms | 1.09 | 0.05 | 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 'SIMD.RayTracerBench*'
```

### SIMD.RayTracerBench.Bench

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in Inlining.InlineGCStruct

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

[WithFormat - Duration of single invocation]()
📝 - [Benchmark Source]()
[ADX - Test Multi Config Graph]()

| 0.27 ns | 1.63 ns | 6.00 | 0.04 | 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 'Inlining.InlineGCStruct*'
```

### Inlining.InlineGCStruct.WithFormat

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

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Assessment

This issue has not been assessed yet.

[Perf] Linux/x64: 23 Regressions on 1/22/2026 3:57:05 AM +00:00

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