[Perf] Windows/x64: 2 Improvements on 7/20/2026 12:31:27 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [c1b09d933f7d720f7ae50f80b4ec6980bb93d96f](https://github.com/dotnet/runtime/commit/c1b09d933f7d720f7ae50f80b4ec6980bb93d96f)
Compare | [630a7009ba484fe96b8f0b81e2f4cc0bb6827903](https://github.com/dotnet/runtime/commit/630a7009ba484fe96b8f0b81e2f4cc0bb6827903)
Diff | [Diff](https://github.com/dotnet/runtime/compare/c1b09d933f7d720f7ae50f80b4ec6980bb93d96f...630a7009ba484fe96b8f0b81e2f4cc0bb6827903)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Memory.Span<Char>

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

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

| 22.84 ns | 14.18 ns | 0.62 | 0.47 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Memory.Span*'
```

### System.Memory.Span<Char>.Reverse(Size: 512)

#### 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 | Windows 10.0.22631
Queue | ViperWindows
Baseline | [c536338d89a6ccc0bcbca46e44e3343d990e06aa](https://github.com/dotnet/runtime/commit/c536338d89a6ccc0bcbca46e44e3343d990e06aa)
Compare | [630a7009ba484fe96b8f0b81e2f4cc0bb6827903](https://github.com/dotnet/runtime/commit/630a7009ba484fe96b8f0b81e2f4cc0bb6827903)
Diff | [Diff](https://github.com/dotnet/runtime/compare/c536338d89a6ccc0bcbca46e44e3343d990e06aa...630a7009ba484fe96b8f0b81e2f4cc0bb6827903)
Configs | CompilationMode:tiered, RunKind:micro

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

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

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

| 156.46 ns | 132.82 ns | 0.85 | 0.52 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.Json.Serialization.Tests.WriteJson*'
```

### System.Text.Json.Serialization.Tests.WriteJson<LoginViewModel>.SerializeToString(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.Memory/Span.cs:56-57 and System.Text.Json/Serializer/WriteJson.cs:75-76, then run the provided benchmarks_ci.py filters. Compare the reported Windows results with the linked baseline and test reports. Done requires confirming whether these improvements need a runtime change or are expected performance data.

Written by the indexing model from the issue text.