dotnet / dotnet/perf-autofiling-issues

[Perf] Linux/x64: 6 Regressions on 7/23/2026 8:26:45 AM +00:00

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

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [dc3757e67b2d6eb7d6db7e052574a02c3d445432](https://github.com/dotnet/runtime/commit/dc3757e67b2d6eb7d6db7e052574a02c3d445432)
Compare | [7ffec088158c895276b85cf176e37904f7d53a56](https://github.com/dotnet/runtime/commit/7ffec088158c895276b85cf176e37904f7d53a56)
Diff | [Diff](https://github.com/dotnet/runtime/compare/dc3757e67b2d6eb7d6db7e052574a02c3d445432...7ffec088158c895276b85cf176e37904f7d53a56)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Buffers.Text.Tests.Base64Tests

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

  • [Base64DecodeDestinationTooSmall - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 598.47 ns | 1446.81 ns | 2.42 | 0.01 | False | | |
|
  • [ConvertTryFromBase64Chars - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 936.05 ns | 1732.26 ns | 1.85 | 0.01 | False | | |
|
  • [ConvertToBase64CharArray - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 737.17 ns | 889.41 ns | 1.21 | 0.01 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Buffers.Text.Tests.Base64Tests*'
```

### System.Buffers.Text.Tests.Base64Tests.Base64DecodeDestinationTooSmall(NumberOfBytes: 1000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Buffers.Text.Tests.Base64Tests.ConvertTryFromBase64Chars(NumberOfBytes: 1000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Buffers.Text.Tests.Base64Tests.ConvertToBase64CharArray(NumberOfBytes: 1000)

#### 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 | [dc3757e67b2d6eb7d6db7e052574a02c3d445432](https://github.com/dotnet/runtime/commit/dc3757e67b2d6eb7d6db7e052574a02c3d445432)
Compare | [7ffec088158c895276b85cf176e37904f7d53a56](https://github.com/dotnet/runtime/commit/7ffec088158c895276b85cf176e37904f7d53a56)
Diff | [Diff](https://github.com/dotnet/runtime/compare/dc3757e67b2d6eb7d6db7e052574a02c3d445432...7ffec088158c895276b85cf176e37904f7d53a56)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Text.Json.Reader.Tests.Perf_Base64

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

  • [ReadBase64EncodedByteArray_NoEscaping - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 1.16 μs | 2.26 μs | 1.94 | 0.01 | False | | |
|
  • [ReadBase64EncodedByteArray_NoEscaping - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 200.18 ns | 326.89 ns | 1.63 | 0.08 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.Json.Reader.Tests.Perf_Base64*'
```

### System.Text.Json.Reader.Tests.Perf_Base64.ReadBase64EncodedByteArray_NoEscaping(NumberOfBytes: 1000)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Reader.Tests.Perf_Base64.ReadBase64EncodedByteArray_NoEscaping(NumberOfBytes: 100)

#### 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 | [dc3757e67b2d6eb7d6db7e052574a02c3d445432](https://github.com/dotnet/runtime/commit/dc3757e67b2d6eb7d6db7e052574a02c3d445432)
Compare | [7ffec088158c895276b85cf176e37904f7d53a56](https://github.com/dotnet/runtime/commit/7ffec088158c895276b85cf176e37904f7d53a56)
Diff | [Diff](https://github.com/dotnet/runtime/compare/dc3757e67b2d6eb7d6db7e052574a02c3d445432...7ffec088158c895276b85cf176e37904f7d53a56)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Perf_Convert

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

  • [FromBase64Chars - Duration of single invocation]()
  • 📝 - [Benchmark Source]()
  • [ADX - Test Multi Config Graph]()
| 75.78 ns | 102.27 ns | 1.35 | 0.06 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Perf_Convert*'
```

### System.Perf_Convert.FromBase64Chars

#### 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 benchmark sources at src/benchmarks/micro/libraries/System.Buffers/Base64Tests.cs and src/benchmarks/micro/libraries/System.Text.Json/Utf8JsonReader/Perf.Base64.cs. Compare the baseline and test commits, then run the documented benchmarks_ci.py command with the Base64 filter. Done means the reported WebAssembly AOT regressions are explained and the affected benchmark results no longer regress.

Written by the indexing model from the issue text.

Assessment

Tech stack
python, wasm
Domain
performance, testing-qa
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
38/100

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