[Perf] Windows/x86: 3 Regressions on 8/7/2026 7:09:09 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [9bf3be3ad48e77e97436fa96825cb713a6964389](https://github.com/dotnet/runtime/commit/9bf3be3ad48e77e97436fa96825cb713a6964389)
Compare | [4c86c57ac3a6569063da4cb0a7245aadbc276f00](https://github.com/dotnet/runtime/commit/4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Diff | [Diff](https://github.com/dotnet/runtime/compare/9bf3be3ad48e77e97436fa96825cb713a6964389...4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.Tests.Perf_FileStream

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

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

| 169.35 μs | 403.49 μs | 2.38 | 0.67 | 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.IO.Tests.Perf_FileStream*'
```

### System.IO.Tests.Perf_FileStream.ReadAsync_NoBuffering(fileSize: 1048576, userBufferSize: 16384, options: None)

#### 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 | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [9bf3be3ad48e77e97436fa96825cb713a6964389](https://github.com/dotnet/runtime/commit/9bf3be3ad48e77e97436fa96825cb713a6964389)
Compare | [4c86c57ac3a6569063da4cb0a7245aadbc276f00](https://github.com/dotnet/runtime/commit/4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Diff | [Diff](https://github.com/dotnet/runtime/compare/9bf3be3ad48e77e97436fa96825cb713a6964389...4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Linq.Tests.Perf_Enumerable

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

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

| 381.25 ns | 410.93 ns | 1.08 | 0.49 | 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.Linq.Tests.Perf_Enumerable*'
```

### System.Linq.Tests.Perf_Enumerable.SelectToList(input: IList)

#### 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 | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [9bf3be3ad48e77e97436fa96825cb713a6964389](https://github.com/dotnet/runtime/commit/9bf3be3ad48e77e97436fa96825cb713a6964389)
Compare | [4c86c57ac3a6569063da4cb0a7245aadbc276f00](https://github.com/dotnet/runtime/commit/4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Diff | [Diff](https://github.com/dotnet/runtime/compare/9bf3be3ad48e77e97436fa96825cb713a6964389...4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in Interop.ComWrappersTests

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

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

| 692.80 ms | 1271.34 ms | 1.84 | 0.27 | 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 'Interop.ComWrappersTests*'
```

### Interop.ComWrappersTests.ParallelRCWLookUp

#### 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 at src/benchmarks/micro/libraries/System.IO.FileSystem/Perf.FileStream.cs, src/benchmarks/micro/libraries/System.Linq/Perf.Enumerable.cs, and src/benchmarks/micro/runtime/Interop/ComWrappers.cs. Run the listed benchmarks with the provided filters, then compare the baseline and compare commits; done means the reported x86 Windows regressions are reproduced and their cause is identified.

Written by the indexing model from the issue text.