[Perf] Linux/x64: 2 Regressions on 7/13/2026 5:42:28 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [8ba3455391cc51b9f639ba5baef5394b2d219050](https://github.com/dotnet/runtime/commit/8ba3455391cc51b9f639ba5baef5394b2d219050)
Compare | [a90733cc40d6c7037a37d9c2b5c2403b8cac490f](https://github.com/dotnet/runtime/commit/a90733cc40d6c7037a37d9c2b5c2403b8cac490f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/8ba3455391cc51b9f639ba5baef5394b2d219050...a90733cc40d6c7037a37d9c2b5c2403b8cac490f)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.Text.Json.Serialization.Tests.WriteJson<LoginViewModel>

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

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

| 26.82 μs | 35.81 μs | 1.34 | 0.31 | False | | |
|

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

| 64.42 μs | 75.83 μs | 1.18 | 0.19 | 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.Serialization.Tests.WriteJson*'
```

### System.Text.Json.Serialization.Tests.WriteJson<LoginViewModel>.SerializeToWriter(Mode: Reflection)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Serialization.Tests.WriteJson<LoginViewModel>.SerializeObjectProperty(Mode: Reflection)

#### 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)

Start with the benchmark source at src/benchmarks/micro/libraries/System.Text.Json/Serializer/WriteJson.cs:81-87 and 97-98, then read the linked test report and benchmarking workflow. Run the provided benchmarks_ci.py filter for WriteJson and compare the two listed results with the baseline and comparison commits; done means the regression is explained and the affected benchmark behavior is addressed.

Written by the indexing model from the issue text.