[Perf] Linux/x64: 2 Improvements on 9/3/2026 9:59:06 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [334cc5c43dfb4b6acab5052c15ee8b1631d069bc](https://github.com/dotnet/runtime/commit/334cc5c43dfb4b6acab5052c15ee8b1631d069bc)
Compare | [134de00ac5934568c582a35322ae16a228db430d](https://github.com/dotnet/runtime/commit/134de00ac5934568c582a35322ae16a228db430d)
Diff | [Diff](https://github.com/dotnet/runtime/compare/334cc5c43dfb4b6acab5052c15ee8b1631d069bc...134de00ac5934568c582a35322ae16a228db430d)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Numerics.Tests.Perf_VectorConvert

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

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

| 591.69 ns | 550.31 ns | 0.93 | 0.00 | 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.Numerics.Tests.Perf_VectorConvert*'
```

### System.Numerics.Tests.Perf_VectorConvert.Narrow_uint

#### 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 | [334cc5c43dfb4b6acab5052c15ee8b1631d069bc](https://github.com/dotnet/runtime/commit/334cc5c43dfb4b6acab5052c15ee8b1631d069bc)
Compare | [134de00ac5934568c582a35322ae16a228db430d](https://github.com/dotnet/runtime/commit/134de00ac5934568c582a35322ae16a228db430d)
Diff | [Diff](https://github.com/dotnet/runtime/compare/334cc5c43dfb4b6acab5052c15ee8b1631d069bc...134de00ac5934568c582a35322ae16a228db430d)
Configs | CompilationMode:tiered, RunKind:micro

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

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]()

| 49.17 ns | 45.03 ns | 0.92 | 0.22 | 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.Text.Json.Serialization.Tests.WriteJson>*'
```

### System.Text.Json.Serialization.Tests.WriteJson<Nullable<DateTimeOffset>>.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 sources at src/benchmarks/micro/libraries/System.Numerics.Vectors/Perf_VectorConvert.cs and src/benchmarks/micro/libraries/System.Text.Json/Serializer/WriteJson.cs, then review the linked performance reports. Run the provided benchmarks_ci.py commands to reproduce the measurements; done requires a clear explanation or actionable follow-up for the reported improvements.

Written by the indexing model from the issue text.