dotnet / dotnet/perf-autofiling-issues

[Perf] Windows/x86: 20 Regressions on 6/24/2026 7:31:32 AM +00:00

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arch-x86 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 | [0d1a20fb14109f277df06ebee3f83c964f9dcc61](https://github.com/dotnet/runtime/commit/0d1a20fb14109f277df06ebee3f83c964f9dcc61)
Compare | [e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7](https://github.com/dotnet/runtime/commit/e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
Diff | [Diff](https://github.com/dotnet/runtime/compare/0d1a20fb14109f277df06ebee3f83c964f9dcc61...e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Text.Json.Tests.Perf_Reader

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

  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 75.70 ns | 102.77 ns | 1.36 | 0.08 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 68.48 ns | 88.95 ns | 1.30 | 0.03 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 619.52 ns | 786.22 ns | 1.27 | 0.03 | False | | |
|
  • [ReadReturnBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 77.93 ns | 96.22 ns | 1.23 | 0.03 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 113.07 ns | 128.09 ns | 1.13 | 0.02 | False | | |
|
  • [ReadReturnBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 2.21 μs | 2.50 μs | 1.13 | 0.01 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.91 μs | 2.14 μs | 1.12 | 0.00 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.89 μs | 2.12 μs | 1.12 | 0.01 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 562.76 ns | 613.54 ns | 1.09 | 0.06 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 551.56 ns | 590.17 ns | 1.07 | 0.04 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.27 μs | 1.35 μs | 1.06 | 0.03 | False | | |

![graph]()
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[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.Text.Json.Tests.Perf_Reader*'
```

### System.Text.Json.Tests.Perf_Reader.ReadSingleSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: HelloWorld)

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### System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop(IsDataCompact: False, TestCase: HelloWorld)

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### System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: Json400B)

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### System.Text.Json.Tests.Perf_Reader.ReadReturnBytes(IsDataCompact: False, TestCase: HelloWorld)

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### System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: HelloWorld)

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### System.Text.Json.Tests.Perf_Reader.ReadReturnBytes(IsDataCompact: False, TestCase: LotsOfNumbers)

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### System.Text.Json.Tests.Perf_Reader.ReadSingleSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: LotsOfNumbers)

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### System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop(IsDataCompact: False, TestCase: LotsOfNumbers)

#### ETL Files

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### System.Text.Json.Tests.Perf_Reader.ReadSingleSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: Json400B)

#### ETL Files

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### System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop(IsDataCompact: False, TestCase: Json400B)

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### System.Text.Json.Tests.Perf_Reader.ReadSingleSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: LotsOfStrings)

#### ETL Files

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#### 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 | [e3ecd30e4d6bfeedec6b4730c8ef87951cfe1f17](https://github.com/dotnet/runtime/commit/e3ecd30e4d6bfeedec6b4730c8ef87951cfe1f17)
Compare | [e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7](https://github.com/dotnet/runtime/commit/e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
Diff | [Diff](https://github.com/dotnet/runtime/compare/e3ecd30e4d6bfeedec6b4730c8ef87951cfe1f17...e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
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 - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 2.49 ms | 4.18 ms | 1.68 | 0.71 | False | | |
|
  • [ReadAsync - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 4.37 ms | 5.68 ms | 1.30 | 0.64 | False | | |
|
  • [FlushAsync - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 10.44 ms | 13.40 ms | 1.28 | 0.59 | False | | |
|
  • [ReadAsync - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 4.17 ms | 5.03 ms | 1.21 | 0.60 | False | | |
|
  • [WriteAsync - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 3.45 ms | 4.17 ms | 1.21 | 0.75 | False | | |

![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.Tests.Perf_FileStream*'
```

### System.IO.Tests.Perf_FileStream.ReadAsync(fileSize: 1048576, userBufferSize: 512, options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.Perf_FileStream.ReadAsync(fileSize: 1048576, userBufferSize: 4096, options: Asynchronous)

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

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### System.IO.Tests.Perf_FileStream.ReadAsync(fileSize: 1048576, userBufferSize: 512, options: Asynchronous)

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### System.IO.Tests.Perf_FileStream.WriteAsync(fileSize: 1048576, userBufferSize: 512, options: None)

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#### 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 | [0d1a20fb14109f277df06ebee3f83c964f9dcc61](https://github.com/dotnet/runtime/commit/0d1a20fb14109f277df06ebee3f83c964f9dcc61)
Compare | [e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7](https://github.com/dotnet/runtime/commit/e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
Diff | [Diff](https://github.com/dotnet/runtime/compare/0d1a20fb14109f277df06ebee3f83c964f9dcc61...e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Text.Json.Document.Tests.Perf_DocumentParse

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

  • [Parse - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 126.38 ns | 144.71 ns | 1.15 | 0.03 | False | | |
|
  • [Parse - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 797.44 ns | 886.15 ns | 1.11 | 0.01 | False | | |
|
  • [Parse - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 174.42 ns | 193.00 ns | 1.11 | 0.04 | False | | |
|
  • [Parse - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.24 μs | 1.32 μs | 1.06 | 0.02 | 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.Text.Json.Document.Tests.Perf_DocumentParse*'
```

### System.Text.Json.Document.Tests.Perf_DocumentParse.Parse(IsDataIndented: True, TestRandomAccess: False, TestCase: HelloWorld)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Document.Tests.Perf_DocumentParse.Parse(IsDataIndented: True, TestRandomAccess: False, TestCase: BasicJson)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Document.Tests.Perf_DocumentParse.Parse(IsDataIndented: True, TestRandomAccess: True, TestCase: HelloWorld)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Document.Tests.Perf_DocumentParse.Parse(IsDataIndented: True, TestRandomAccess: True, TestCase: BasicJson)

#### 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 performance report and the linked benchmark source at performance/src/benchmarks/micro/libraries/System.Text.Json/Utf8JsonReader/Perf.Reader.cs, especially the listed reader benchmarks. Compare the baseline and test commits, then reproduce the Windows/x86 tiered microbenchmark run. Done means identifying the cause of the reported regressions and confirming the affected measurements no longer regress.

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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