[Perf] Windows/x86: 12 Regressions on 7/27/2026 11:29:43 AM +00:00

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#77,232 opened on Aug 4, 2026 1 comment 0 reactions 0 assignees View on GitHub

arch-x86 branch-refs/heads/main compilationmode-tiered kind-micro Look Again 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 | [2aa2ce008a33a25ac77f4f340b628e135b94087f](https://github.com/dotnet/runtime/commit/2aa2ce008a33a25ac77f4f340b628e135b94087f)
Compare | [da6081391e5d3227e462c082b345af8720db05c1](https://github.com/dotnet/runtime/commit/da6081391e5d3227e462c082b345af8720db05c1)
Diff | [Diff](https://github.com/dotnet/runtime/compare/2aa2ce008a33a25ac77f4f340b628e135b94087f...da6081391e5d3227e462c082b345af8720db05c1)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Net.Http.Tests.SocketsHttpHandlerPerfTest

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

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

| 23.39 μs | 37.08 μs | 1.59 | 0.33 | False | | |
|

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

| 27.68 μs | 42.72 μs | 1.54 | 0.60 | False | | |
|

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

| 27.67 μs | 42.45 μs | 1.53 | 0.39 | False | | |

![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.Net.Http.Tests.SocketsHttpHandlerPerfTest*'
```

### System.Net.Http.Tests.SocketsHttpHandlerPerfTest.Get_EnumerateHeaders_Validated(ssl: False, chunkedResponse: True, responseLength: 1)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Net.Http.Tests.SocketsHttpHandlerPerfTest.Get_EnumerateHeaders_Validated(ssl: True, chunkedResponse: False, responseLength: 1)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Net.Http.Tests.SocketsHttpHandlerPerfTest.Get_EnumerateHeaders_Validated(ssl: True, chunkedResponse: True, responseLength: 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

### Regressions in System.Collections.Tests.Perf_BitArray

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

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

| 9.07 ns | 13.82 ns | 1.52 | 0.32 | False | | |
|

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

| 9.12 ns | 13.37 ns | 1.47 | 0.30 | False | | |
|

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

| 10.94 ns | 12.04 ns | 1.10 | 0.02 | False | | |

![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.Collections.Tests.Perf_BitArray*'
```

### System.Collections.Tests.Perf_BitArray.BitArrayXor(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.Tests.Perf_BitArray.BitArrayOr(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.Tests.Perf_BitArray.BitArraySetLengthShrink(Size: 4)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

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

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

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

| 25.98 ns | 32.80 ns | 1.26 | 0.42 | False | | |
|

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

| 25.54 ns | 29.89 ns | 1.17 | 0.40 | 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.Numerics.Tensors.Tests.Perf_NumberTensorPrimitives*'
```

### System.Numerics.Tensors.Tests.Perf_NumberTensorPrimitives<Double>.MaxMagnitude_Vector(BufferLength: 128)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Numerics.Tensors.Tests.Perf_NumberTensorPrimitives<Double>.AddMultiply_ScalarAddend(BufferLength: 128)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Threading.Tests.Perf_Interlocked

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

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

| 3.86 ns | 898.49 ns | 232.90 | 0.20 | 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.Threading.Tests.Perf_Interlocked*'
```

### System.Threading.Tests.Perf_Interlocked.CompareExchange_long

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### 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]()

| 40.80 ns | 44.38 ns | 1.09 | 0.42 | 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: 128)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Collections.ContainsTrue<Int32>

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

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

| 6.75 μs | 8.50 μs | 1.26 | 0.14 | 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.ContainsTrue*'
```

### System.Collections.ContainsTrue<Int32>.List(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

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

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

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

| 92.67 ms | 203.05 ms | 2.19 | 0.64 | 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.WriteAsync(fileSize: 104857600, userBufferSize: 4096, options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

Contributor guide

No contributing guide indexed for this repository

Research direction

Start with the linked benchmark sources, including Perf.SocketsHttpHandler.cs and Perf.BitArray.cs, then run the provided benchmarks_ci.py command using the stated x86 Windows configuration. Compare the listed baseline and test commits and inspect the generated performance reports. Done means confirming the regressions and narrowing them to an actionable runtime 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

[Perf] Windows/x86: 12 Regressions on 7/27/2026 11:29:43 AM +00:00

Description

Contributor guide

Research direction

Assessment

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