[Perf] Linux/x64: 1 Regression on 9/13/2026 3:54:51 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [b9678dcc0e7bac74a0d6b669b39d1007359b0016](https://github.com/dotnet/runtime/commit/b9678dcc0e7bac74a0d6b669b39d1007359b0016)
Compare | [3c4631e63b1de4308e2965b149992b992c9f5318](https://github.com/dotnet/runtime/commit/3c4631e63b1de4308e2965b149992b992c9f5318)
Diff | [Diff](https://github.com/dotnet/runtime/compare/b9678dcc0e7bac74a0d6b669b39d1007359b0016...3c4631e63b1de4308e2965b149992b992c9f5318)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile

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

• [CreateNew - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config 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.MemoryMappedFiles.Tests.Perf_MemoryMappedFile*'
```

### System.IO.MemoryMappedFiles.Tests.Perf_MemoryMappedFile.CreateNew(capacity: 10000000)

#### 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.MemoryMappedFiles benchmark source at src/benchmarks/micro/libraries/System.IO.MemoryMappedFiles/Perf.MemoryMappedFile.cs#L24-L25 and the linked test report. Run the provided benchmarks_ci.py command, then compare the baseline and test commits and inspect the regression report. Done means the CreateNew regression is explained and the benchmark returns to the expected performance.

Written by the indexing model from the issue text.