[Perf] Linux/x64: 2 Regressions on 8/25/2026 6:02:39 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [113dfc84608caa4b9a87a302c952bf7f35617240](https://github.com/dotnet/runtime/commit/113dfc84608caa4b9a87a302c952bf7f35617240)
Compare | [8baacb006f5615ebd705bdf9de98ca5df7bf1ba1](https://github.com/dotnet/runtime/commit/8baacb006f5615ebd705bdf9de98ca5df7bf1ba1)
Diff | [Diff](https://github.com/dotnet/runtime/compare/113dfc84608caa4b9a87a302c952bf7f35617240...8baacb006f5615ebd705bdf9de98ca5df7bf1ba1)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

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

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

• [SerializeToUtf8Bytes - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

| 44.52 μs | 51.29 μs | 1.15 | 0.19 | False | | |
|

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

| 32.69 μs | 36.76 μs | 1.12 | 0.20 | 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<StructRecord>.SerializeToUtf8Bytes(Mode: SourceGen)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Serialization.Tests.WriteJson<StructRecord>.SerializeToWriter(Mode: SourceGen)

#### 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 performance/src/benchmarks/micro/libraries/System.Text.Json/Serializer/WriteJson.cs#L78-L87 and reproduce the filtered WriteJson benchmark using the provided benchmarks_ci.py command. Compare the baseline and test commits, then use the linked test report and graphs to determine whether the two reported regressions persist; done means the regression is explained and addressed or clearly triaged with evidence.

Written by the indexing model from the issue text.