[Perf] Linux/arm64: 3 Regressions on 8/10/2026 10:42:08 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [14b601ec5edfeecbc70368890e8676fe5c29da83](https://github.com/dotnet/runtime/commit/14b601ec5edfeecbc70368890e8676fe5c29da83)
Compare | [60108ba66eb7d1d12f595480091b4ad80a24b172](https://github.com/dotnet/runtime/commit/60108ba66eb7d1d12f595480091b4ad80a24b172)
Diff | [Diff](https://github.com/dotnet/runtime/compare/14b601ec5edfeecbc70368890e8676fe5c29da83...60108ba66eb7d1d12f595480091b4ad80a24b172)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.Tests.Perf_FileStream

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

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

| 11.61 μs | 14.95 μs | 1.29 | 0.38 | False | | |
|

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

| 11.17 μs | 12.25 μs | 1.10 | 0.40 | False | | |
|

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

| 6.72 μs | 7.30 μs | 1.09 | 0.60 | False | | |

![graph]()
![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_FileStream*'
```

### System.IO.Tests.Perf_FileStream.SeekForward(fileSize: 1024, options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.Perf_FileStream.SeekForward(fileSize: 1024, options: Asynchronous)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.Perf_FileStream.Read(fileSize: 1024, userBufferSize: 1024, options: Asynchronous)

#### 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_FileStream benchmarks in performance/src/benchmarks/micro/libraries/System.IO.FileSystem/Perf.FileStream.cs, especially the cited SeekForward and Read ranges. Follow the benchmarking workflow and run the provided benchmarks on Linux/arm64, then compare the linked baseline and test reports. Done means the three regressions have an identified cause and a recorded resolution or explanation.

Written by the indexing model from the issue text.