[Perf] Windows/x64: 5 Regressions on 8/28/2026 8:01:56 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [22d4a3b8329dca505095f2b09da0763f52678d8d](https://github.com/dotnet/runtime/commit/22d4a3b8329dca505095f2b09da0763f52678d8d)
Compare | [100da3f94464f99616ee4a401670bec491ebc787](https://github.com/dotnet/runtime/commit/100da3f94464f99616ee4a401670bec491ebc787)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22d4a3b8329dca505095f2b09da0763f52678d8d...100da3f94464f99616ee4a401670bec491ebc787)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.Tests.StringReaderReadLineTests

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

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

| 11.02 μs | 11.77 μs | 1.07 | 0.10 | False | | |
|

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

| 17.30 μs | 18.34 μs | 1.06 | 0.36 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.IO.Tests.StringReaderReadLineTests*'
```

### System.IO.Tests.StringReaderReadLineTests.ReadLine(LineLengthRange: [ 9, 32])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StringReaderReadLineTests.ReadLineAsync(LineLengthRange: [ 9, 32])

#### 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 | Windows 10.0.22631
Queue | ViperWindows
Baseline | [22d4a3b8329dca505095f2b09da0763f52678d8d](https://github.com/dotnet/runtime/commit/22d4a3b8329dca505095f2b09da0763f52678d8d)
Compare | [100da3f94464f99616ee4a401670bec491ebc787](https://github.com/dotnet/runtime/commit/100da3f94464f99616ee4a401670bec491ebc787)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22d4a3b8329dca505095f2b09da0763f52678d8d...100da3f94464f99616ee4a401670bec491ebc787)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in Microsoft.AspNetCore.Server.Kestrel.Performance.PipeThroughputBenchmark

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

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

| 492.61 ns | 1279.87 ns | 2.60 | 0.68 | False | | |
|

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

| 311.41 ns | 763.94 ns | 2.45 | 0.66 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'Microsoft.AspNetCore.Server.Kestrel.Performance.PipeThroughputBenchmark*'
```

### Microsoft.AspNetCore.Server.Kestrel.Performance.PipeThroughputBenchmark.Parse_ParallelAsync(Length: 4096, Chunks: 16)

#### ETL Files

#### Histogram

#### JIT Disasms

### Microsoft.AspNetCore.Server.Kestrel.Performance.PipeThroughputBenchmark.Parse_ParallelAsync(Length: 4096, Chunks: 1)

#### 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 | Windows 10.0.22631
Queue | ViperWindows
Baseline | [22d4a3b8329dca505095f2b09da0763f52678d8d](https://github.com/dotnet/runtime/commit/22d4a3b8329dca505095f2b09da0763f52678d8d)
Compare | [100da3f94464f99616ee4a401670bec491ebc787](https://github.com/dotnet/runtime/commit/100da3f94464f99616ee4a401670bec491ebc787)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22d4a3b8329dca505095f2b09da0763f52678d8d...100da3f94464f99616ee4a401670bec491ebc787)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Collections.CtorFromCollection<String>

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

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

| 146.64 μs | 163.71 μs | 1.12 | 0.35 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.CtorFromCollection*'
```

### System.Collections.CtorFromCollection<String>.SortedDictionary(Size: 512)

#### 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)

Start with the benchmark sources src/benchmarks/micro/libraries/System.IO/StringReaderReadLineTests.cs and src/benchmarks/micro/libraries/System.IO.Pipelines/PipeThroughputBenchmark.cs. Run the provided benchmarks_ci.py commands and compare the reported regressions with the linked baseline and compare commits. Done means identifying the cause of the Windows/x64 performance regressions and confirming the affected benchmarks no longer regress.

Written by the indexing model from the issue text.