dotnet / dotnet/perf-autofiling-issues

[Perf] Linux/x64: 36 Regressions on 6/24/2026 7:31:32 AM +00:00

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arch-wasm arch-x64 branch-refs/heads/main compilationmode-wasm kind-micro Look Again os-linux perf-regression runkind-micro runtimetype-coreclr untriaged
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Description

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
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:wasm, RunKind:micro, RuntimeType:coreclr

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

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

  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.69 ms | 2.28 ms | 1.35 | 0.31 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.18 ms | 1.53 ms | 1.30 | 0.27 | False | | |
|
  • [ReadReturnBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.28 ms | 1.66 ms | 1.29 | 0.30 | False | | |
|
  • [ReadReturnBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 427.35 μs | 539.96 μs | 1.26 | 0.25 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 289.56 μs | 364.23 μs | 1.26 | 0.28 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.64 ms | 2.02 ms | 1.23 | 0.25 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 180.17 μs | 218.73 μs | 1.21 | 0.25 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 344.42 μs | 417.49 μs | 1.21 | 0.31 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 381.41 μs | 460.21 μs | 1.21 | 0.21 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 351.53 μs | 423.64 μs | 1.21 | 0.27 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.72 ms | 2.08 ms | 1.20 | 0.29 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 194.91 μs | 234.46 μs | 1.20 | 0.29 | False | | |
|
  • [ReadSingleSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 283.79 μs | 338.84 μs | 1.19 | 0.28 | False | | |
|
  • [ReadReturnBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 2.14 ms | 2.55 ms | 1.19 | 0.23 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.18 ms | 1.39 ms | 1.18 | 0.27 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.23 ms | 1.43 ms | 1.16 | 0.28 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 302.97 μs | 351.13 μs | 1.16 | 0.31 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.77 ms | 2.02 ms | 1.14 | 0.28 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 180.49 μs | 205.01 μs | 1.14 | 0.25 | False | | |
|
  • [ReadMultiSpanSequenceEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 15.96 ms | 17.92 ms | 1.12 | 0.29 | False | | |
|
  • [ReadSpanEmptyLoop - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 15.98 ms | 17.34 ms | 1.09 | 0.23 | False | | |
|
  • [ReadReturnBytes - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 203.76 μs | 216.58 μs | 1.06 | 0.26 | False | | |

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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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.Json.Tests.Perf_Reader*'
```

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: Json4KB)

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Reader.ReadMultiSpanSequenceEmptyLoop(IsDataCompact: False, TestCase: Json40KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop(IsDataCompact: False, TestCase: Json40KB)

#### ETL Files

#### Histogram

#### JIT Disasms

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

#### 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 | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
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:wasm, RunKind:micro, RuntimeType:coreclr

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

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

  • [ReadMultiSegmentSequenceUsingSpan - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.73 ms | 2.06 ms | 1.19 | 0.30 | False | | |
|
  • [ReadMultiSegmentSequence - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 170.75 ms | 203.28 ms | 1.19 | 0.23 | False | | |
|
  • [ReadMultiSegmentSequence - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 16.76 ms | 19.79 ms | 1.18 | 0.22 | False | | |
|
  • [ReadMultiSegmentSequenceUsingSpan - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 167.94 ms | 196.61 ms | 1.17 | 0.32 | False | | |
|
  • [ReadSingleSegmentSequence - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 16.10 ms | 17.49 ms | 1.09 | 0.32 | False | | |
|
  • [ReadMultiSegmentSequence - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 168.36 ms | 182.48 ms | 1.08 | 0.30 | False | | |
|
  • [ReadMultiSegmentSequence - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.72 ms | 1.85 ms | 1.08 | 0.28 | False | | |
|
  • [ReadSingleSegmentSequenceByN - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.73 ms | 1.85 ms | 1.07 | 0.35 | False | | |
|
  • [ReadSingleSegmentSequence - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 167.24 ms | 178.55 ms | 1.07 | 0.27 | False | | |
|
  • [ReadSingleSegmentSequenceByN - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 167.94 ms | 178.18 ms | 1.06 | 0.22 | False | | |
|
  • [ReadMultiSegmentSequenceUsingSpan - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.73 ms | 1.82 ms | 1.05 | 0.36 | False | | |

![graph]()
![graph]()
![graph]()
![graph]()
![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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.Json.Tests.Perf_Segment*'
```

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequenceUsingSpan(segmentSize: 4096, TestCase: Json4KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequence(segmentSize: 8192, TestCase: Json400KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequence(segmentSize: 8192, TestCase: Json40KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequenceUsingSpan(segmentSize: 8192, TestCase: Json400KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadSingleSegmentSequence(TestCase: Json40KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequence(segmentSize: 4096, TestCase: Json400KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequence(segmentSize: 8192, TestCase: Json4KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadSingleSegmentSequenceByN(numberOfBytes: 8192, TestCase: Json4KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadSingleSegmentSequence(TestCase: Json400KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadSingleSegmentSequenceByN(numberOfBytes: 8192, TestCase: Json400KB)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Tests.Perf_Segment.ReadMultiSegmentSequenceUsingSpan(segmentSize: 8192, TestCase: Json4KB)

#### 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 System.Text.Json benchmark source in src/benchmarks/micro/libraries/System.Text.Json/Utf8JsonReader/Perf.Reader.cs and compare the listed baseline and compare commits. Run the affected Reader benchmarks under the wasm configuration, then trace the regression across the 36 reported cases. Done means the regression is explained and the affected benchmark results no longer regress.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp, wasm
Domain
performance, testing
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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