[Perf] Linux/x64: 2 Improvements on 6/26/2026 6:28:17 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55](https://github.com/dotnet/runtime/commit/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55)
Compare | [207ffd155f96b38be1749584b99f3ac0a505218c](https://github.com/dotnet/runtime/commit/207ffd155f96b38be1749584b99f3ac0a505218c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55...207ffd155f96b38be1749584b99f3ac0a505218c)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Tests.Perf_String

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

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

| 16.62 ns | 15.36 ns | 0.92 | 0.08 | False | | |
|

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

| 16.61 ns | 15.36 ns | 0.92 | 0.12 | 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.Tests.Perf_String*'
```

### System.Tests.Perf_String.ToUpper(s: "TeSt")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_String.ToUpper(s: "test")

#### 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 performance/src/benchmarks/micro/libraries/System.Runtime/Perf.String.cs#L215-L222 and reproduce System.Tests.Perf_String with the documented benchmarks_ci.py command. Review the linked ToUpper reports for the Linux/x64 comparison; the issue does not specify a code change or acceptance criterion, so completion would require triage to define what should be addressed.

Written by the indexing model from the issue text.