[Perf] Linux/x64: 2 Regressions on 9/8/2026 11:42:47 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [335260c10135059cce58b89cf2de024d1cdd8847](https://github.com/dotnet/runtime/commit/335260c10135059cce58b89cf2de024d1cdd8847)
Compare | [ea09718b076f295c3c864d5419fc1a531c09a7df](https://github.com/dotnet/runtime/commit/ea09718b076f295c3c864d5419fc1a531c09a7df)
Diff | [Diff](https://github.com/dotnet/runtime/compare/335260c10135059cce58b89cf2de024d1cdd8847...ea09718b076f295c3c864d5419fc1a531c09a7df)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.Linq.Tests.Perf_Enumerable

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

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

| 2.87 μs | 3.71 μs | 1.29 | 0.22 | False | | |

![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.Linq.Tests.Perf_Enumerable*'
```

### System.Linq.Tests.Perf_Enumerable.SequenceEqual(input1: Array, input2: Array)

#### 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)

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [335260c10135059cce58b89cf2de024d1cdd8847](https://github.com/dotnet/runtime/commit/335260c10135059cce58b89cf2de024d1cdd8847)
Compare | [ea09718b076f295c3c864d5419fc1a531c09a7df](https://github.com/dotnet/runtime/commit/ea09718b076f295c3c864d5419fc1a531c09a7df)
Diff | [Diff](https://github.com/dotnet/runtime/compare/335260c10135059cce58b89cf2de024d1cdd8847...ea09718b076f295c3c864d5419fc1a531c09a7df)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

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

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

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

| 5.54 ms | 6.74 ms | 1.22 | 0.27 | False | | |

![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.Read(fileSize: 1048576, userBufferSize: 512, options: None)

#### 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 sources at src/benchmarks/micro/libraries/System.Linq/Perf.Enumerable.cs#L416-L419 and src/benchmarks/micro/libraries/System.IO.FileSystem/Perf.FileStream.cs#L199-L202, then run the provided benchmarks_ci.py filters on Ubuntu. Compare the reported results with the linked baseline and test commits; done means identifying and addressing the causes of both regressions, with benchmark results no longer showing the reported slowdown.

Written by the indexing model from the issue text.