dotnet / dotnet/perf-autofiling-issues

[Perf] Windows/x86: 6 Regressions on 5/20/2026 1:12:20 AM +00:00

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arch-x86 bdn-update branch-refs/heads/main compilationmode-tiered kind-micro os-windows perf-regression runkind-micro runtime-coreclr untriaged
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Description

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [c6a8e4caf07c58141038ca47aedc61ff39d33d96](https://github.com/dotnet/runtime/commit/c6a8e4caf07c58141038ca47aedc61ff39d33d96)
Compare | [b129b7c103a567531537d2256e58aaa1dc76dbdf](https://github.com/dotnet/runtime/commit/b129b7c103a567531537d2256e58aaa1dc76dbdf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/c6a8e4caf07c58141038ca47aedc61ff39d33d96...b129b7c103a567531537d2256e58aaa1dc76dbdf)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in PerfLabTests.LowLevelPerf

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

  • [InterfaceInterfaceMethodLongHierarchy - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 270.93 μs | 325.10 μs | 1.20 | 0.42 | False | | |
|
  • [ForeachOverList100Elements - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 3.91 ms | 4.14 ms | 1.06 | 0.00 | 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 'PerfLabTests.LowLevelPerf*'
```

### PerfLabTests.LowLevelPerf.InterfaceInterfaceMethodLongHierarchy

#### ETL Files

#### Histogram

#### JIT Disasms

### PerfLabTests.LowLevelPerf.ForeachOverList100Elements

#### 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 | [c6a8e4caf07c58141038ca47aedc61ff39d33d96](https://github.com/dotnet/runtime/commit/c6a8e4caf07c58141038ca47aedc61ff39d33d96)
Compare | [b129b7c103a567531537d2256e58aaa1dc76dbdf](https://github.com/dotnet/runtime/commit/b129b7c103a567531537d2256e58aaa1dc76dbdf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/c6a8e4caf07c58141038ca47aedc61ff39d33d96...b129b7c103a567531537d2256e58aaa1dc76dbdf)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Memory.Span<Char>

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

  • [Reverse - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 86.05 ns | 94.22 ns | 1.09 | 0.53 | False | | |
|
  • [ToArray - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 225.83 ns | 239.63 ns | 1.06 | 0.05 | 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.Memory.Span*'
```

### System.Memory.Span<Char>.Reverse(Size: 3000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Char>.ToArray(Size: 3000)

#### 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 | [907596760ed73c4025395ee502ea7b3c1d285d9e](https://github.com/dotnet/runtime/commit/907596760ed73c4025395ee502ea7b3c1d285d9e)
Compare | [b129b7c103a567531537d2256e58aaa1dc76dbdf](https://github.com/dotnet/runtime/commit/b129b7c103a567531537d2256e58aaa1dc76dbdf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/907596760ed73c4025395ee502ea7b3c1d285d9e...b129b7c103a567531537d2256e58aaa1dc76dbdf)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Numerics.Tensors.Tests.Perf_FloatingPointTensorPrimitives<Double>

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

  • [FusedMultiplyAdd_Vectors - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 887.67 ns | 934.78 ns | 1.05 | 0.34 | 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.Numerics.Tensors.Tests.Perf_FloatingPointTensorPrimitives*'
```

### System.Numerics.Tensors.Tests.Perf_FloatingPointTensorPrimitives<Double>.FusedMultiplyAdd_Vectors(BufferLength: 3079)

#### 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 | [c6a8e4caf07c58141038ca47aedc61ff39d33d96](https://github.com/dotnet/runtime/commit/c6a8e4caf07c58141038ca47aedc61ff39d33d96)
Compare | [b129b7c103a567531537d2256e58aaa1dc76dbdf](https://github.com/dotnet/runtime/commit/b129b7c103a567531537d2256e58aaa1dc76dbdf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/c6a8e4caf07c58141038ca47aedc61ff39d33d96...b129b7c103a567531537d2256e58aaa1dc76dbdf)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Numerics.Tensors.Tests.Perf_NumberTensorPrimitives<Double>

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

  • [Max_Vector - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 670.16 ns | 906.02 ns | 1.35 | 0.36 | 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.Numerics.Tensors.Tests.Perf_NumberTensorPrimitives*'
```

### System.Numerics.Tensors.Tests.Perf_NumberTensorPrimitives<Double>.Max_Vector(BufferLength: 3079)

#### 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 by running the documented benchmarks_ci.py commands for PerfLabTests.LowLevelPerf and System.Memory.Span, then inspect the named sources LowLevelPerf.cs, Span.cs, and Perf_FloatingPointTensorPrimitives.cs. Compare the reported baseline and test commits and use the linked reports to investigate the Windows x86 regressions. Done means identifying the regression cause and validating the performance result after the relevant change.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp
Domain
performance
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Needs clarification
Newbie friendliness
35/100

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