[Perf] Linux/arm64: 2 Improvements on 6/24/2026 8:46:56 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7](https://github.com/dotnet/runtime/commit/e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7)
Compare | [cd27dcec16016aa54be6a09962d1b509150cf99b](https://github.com/dotnet/runtime/commit/cd27dcec16016aa54be6a09962d1b509150cf99b)
Diff | [Diff](https://github.com/dotnet/runtime/compare/e3cbc00cd3e0b511ad36dc240010eb2b9eefc3b7...cd27dcec16016aa54be6a09962d1b509150cf99b)
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
-- | -- | -- | -- | -- | -- | -- | -- | --
|

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

| 208.28 ns | 195.13 ns | 0.94 | 0.19 | False | | |
|

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

| 141.12 ns | 132.83 ns | 0.94 | 0.18 | 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
py .\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>.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 src/benchmarks/micro/libraries/System.Text.Json/Serializer/WriteJson.cs at the linked benchmark lines, then run the provided benchmarks_ci.py command for the WriteJson filter. Compare the ARM64 AzureLinux report and baseline/compare data to determine whether the improvement is reproducible and what changed; done means the result is explained and validated.

Written by the indexing model from the issue text.