dotnet / dotnet/perf-autofiling-issues

[Perf] Windows/x86: 12 Regressions on 3/9/2026 5:24:50 PM +00:00

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arch-x86 branch-refs/heads/main kind-micro os-windows perf-regression runtime-coreclr untriaged
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Description

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82](https://github.com/dotnet/runtime/commit/e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82)
Compare | [e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f](https://github.com/dotnet/runtime/commit/e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82...e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f)
Configs | CompilationMode:tiered, RunKind:micro

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

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

  • [ReadAllBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 14.98 μs | 18.08 μs | 1.21 | 0.07 | 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_File*'
```

### System.IO.Tests.Perf_File.ReadAllBytes(size: 16384)

#### 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 | [e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82](https://github.com/dotnet/runtime/commit/e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82)
Compare | [e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f](https://github.com/dotnet/runtime/commit/e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82...e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile

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

  • [CreateFromFile_Read - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 21.75 μs | 25.56 μs | 1.17 | 0.24 | False | | |
|
  • [CreateFromFile_Read - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 23.24 μs | 26.51 μs | 1.14 | 0.25 | False | | |
|
  • [CreateFromFile - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 39.03 μs | 41.63 μs | 1.07 | 0.31 | False | | |
|
  • [CreateFromFile - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 27.12 μs | 31.39 μs | 1.16 | 0.21 | False | | |
|
  • [CreateFromFile_Read - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 23.63 μs | 27.38 μs | 1.16 | 0.34 | False | | |
|
  • [CreateFromFile_Read - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 21.24 μs | 23.42 μs | 1.10 | 0.30 | False | | |
|
  • [CreateFromFile - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 28.65 μs | 30.64 μs | 1.07 | 0.25 | False | | |

![graph]()
![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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile*'
```

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile_Read(capacity: 10000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile_Read(capacity: 1000000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile(capacity: 10000000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile(capacity: 10000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile_Read(capacity: 10000000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile_Read(capacity: 100000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateFromFile(capacity: 1000000)

#### 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 | [e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82](https://github.com/dotnet/runtime/commit/e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82)
Compare | [e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f](https://github.com/dotnet/runtime/commit/e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/e9ec642ee7ab11ffe1b8e767809fe60dd4a45b82...e3b528cdef1842fc57d4a353ecfe4e34e13b7b4f)
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
-- | -- | -- | -- | -- | -- | -- | -- | --
|

  • [Read - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 12.61 μs | 15.75 μs | 1.25 | 0.13 | False | | |
|
  • [LockUnlock - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 18.14 μs | 23.07 μs | 1.27 | 0.26 | False | | |
|
  • [LockUnlock - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 16.73 μs | 19.96 μs | 1.19 | 0.29 | False | | |
|
  • [ReadByte - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 20.59 μs | 23.80 μs | 1.16 | 0.21 | False | | |

![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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.IO.Tests.Perf_FileStream*'
```

### System.IO.Tests.Perf_FileStream.Read(fileSize: 1024, userBufferSize: 1024, options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.Perf_FileStream.LockUnlock(fileSize: 1024, options: Asynchronous)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.Perf_FileStream.LockUnlock(fileSize: 1024, options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.Perf_FileStream.ReadByte(fileSize: 1024, options: Asynchronous)

#### 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)

Contributor guide

No contributing guide indexed for this repository

Research direction

Start with the linked benchmark sources in dotnet/performance: src/benchmarks/micro/libraries/System.IO.FileSystem/Perf.File.cs (lines 124–131) and src/benchmarks/micro/libraries/System.IO.MemoryMappedFiles/Perf.MemoryMappedFile.cs (lines 30–48). Follow the documented profiling and benchmarking workflows and compare the listed baseline and comparison commits on Windows x86. Done means identifying and addressing the regression, then confirming the affected benchmarks no longer regress.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp
Domain
performance, testing-qa
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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