[Perf] Linux/x64: 1 Regression on 8/5/2026 11:16:49 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [173e6b40e02cd1652102c09e07bd4cf7320b3d4d](https://github.com/dotnet/runtime/commit/173e6b40e02cd1652102c09e07bd4cf7320b3d4d)
Compare | [ecc21b8a08df017dbe4d92e81191a028213d418e](https://github.com/dotnet/runtime/commit/ecc21b8a08df017dbe4d92e81191a028213d418e)
Diff | [Diff](https://github.com/dotnet/runtime/compare/173e6b40e02cd1652102c09e07bd4cf7320b3d4d...ecc21b8a08df017dbe4d92e81191a028213d418e)
Configs | CompilationMode:wasm, RunKind:micro

### Regressions in System.IO.Tests.Perf_File

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

• [WriteAllBytes - 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.Tests.Perf_File*'
```

### System.IO.Tests.Perf_File.WriteAllBytes(size: 104857600)

#### 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.Perf_File.WriteAllBytes benchmark source at src/benchmarks/micro/libraries/System.IO.FileSystem/Perf.File.cs#L84-L#90 and compare the baseline and compare commits. Reproduce with the provided benchmarks_ci.py command and inspect the linked test report and history graph. Done means identifying and addressing the cause of the Linux/x64 WebAssembly regression, then confirming the benchmark no longer regresses.

Written by the indexing model from the issue text.