[Perf] Linux/x64: 2 Improvements on 8/4/2026 3:42:07 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [80aa3f8c5a2d33664fbedafd2f2bb18fdeb8002f](https://github.com/dotnet/runtime/commit/80aa3f8c5a2d33664fbedafd2f2bb18fdeb8002f)
Compare | [f107b2325cccfd453f9bf46013159f4704ea56c2](https://github.com/dotnet/runtime/commit/f107b2325cccfd453f9bf46013159f4704ea56c2)
Diff | [Diff](https://github.com/dotnet/runtime/compare/80aa3f8c5a2d33664fbedafd2f2bb18fdeb8002f...f107b2325cccfd453f9bf46013159f4704ea56c2)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Text.Json.Serialization.Tests.WriteJson<Hashtable>

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

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

| 4.62 μs | 4.03 μs | 0.87 | 0.16 | False | | |
|

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

| 4.61 μs | 4.05 μs | 0.88 | 0.15 | 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<Hashtable>.SerializeToStream(Mode: Reflection)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.Json.Serialization.Tests.WriteJson<Hashtable>.SerializeToStream(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 src/benchmarks/micro/libraries/System.Text.Json/Serializer/WriteJson.cs#L89-L95 and review the linked performance report for WriteJson. Run the provided benchmarks_ci.py filter on Ubuntu 22.04, then investigate the reported Reflection and SourceGen timings; done means the benchmark result is understood and any justified performance change is validated.

Written by the indexing model from the issue text.