[Perf] Linux/arm64: 2 Improvements on 8/12/2026 11:59:15 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [19a2d977ed14ff9ab7417519f0257b3b296a82f4](https://github.com/dotnet/runtime/commit/19a2d977ed14ff9ab7417519f0257b3b296a82f4)
Compare | [63ae268826a5091dfc89baa49844df1aed874a95](https://github.com/dotnet/runtime/commit/63ae268826a5091dfc89baa49844df1aed874a95)
Diff | [Diff](https://github.com/dotnet/runtime/compare/19a2d977ed14ff9ab7417519f0257b3b296a82f4...63ae268826a5091dfc89baa49844df1aed874a95)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.IO.Tests.StringReaderReadToEndTests

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

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

| 13.89 ns | 10.07 ns | 0.73 | 0.66 | False | | |
|

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

| 12.07 ns | 10.09 ns | 0.84 | 0.63 | 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.IO.Tests.StringReaderReadToEndTests*'
```

### System.IO.Tests.StringReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 33, 128])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StringReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 0, 0])

#### 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 System.IO.Tests.StringReaderReadToEndTests.ReadToEnd benchmark source linked at performance/src/benchmarks/micro/libraries/System.IO/StringReaderReadToEndTests.cs#L17-L23 and the reported arm64 Ubuntu results. Follow the benchmarking workflow and run the provided benchmarks_ci.py command to reproduce the measurements. Done means the reported improvement is understood and any resulting runtime performance issue is addressed.

Written by the indexing model from the issue text.