[Perf] Linux/arm64: 3 Regressions on 7/31/2026 12:33:30 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [490a2b069df755f1489170c5ba2a27ce272d1c69](https://github.com/dotnet/runtime/commit/490a2b069df755f1489170c5ba2a27ce272d1c69)
Compare | [ba8afceee83540ed1d867987483f74d4ad2cfae9](https://github.com/dotnet/runtime/commit/ba8afceee83540ed1d867987483f74d4ad2cfae9)
Diff | [Diff](https://github.com/dotnet/runtime/compare/490a2b069df755f1489170c5ba2a27ce272d1c69...ba8afceee83540ed1d867987483f74d4ad2cfae9)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.Tests.BinaryWriterTests

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

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

| 15.54 ns | 17.06 ns | 1.10 | 0.58 | 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.BinaryWriterTests*'
```

### System.IO.Tests.BinaryWriterTests.DefaultCtor

#### 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 | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [7a6987d6e1ca353163a8684054b71693c9db8fc6](https://github.com/dotnet/runtime/commit/7a6987d6e1ca353163a8684054b71693c9db8fc6)
Compare | [ba8afceee83540ed1d867987483f74d4ad2cfae9](https://github.com/dotnet/runtime/commit/ba8afceee83540ed1d867987483f74d4ad2cfae9)
Diff | [Diff](https://github.com/dotnet/runtime/compare/7a6987d6e1ca353163a8684054b71693c9db8fc6...ba8afceee83540ed1d867987483f74d4ad2cfae9)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in MicroBenchmarks.Serializers.Xml_FromStream<LoginViewModel>

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

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

| 4.66 μs | 5.52 μs | 1.19 | 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 'MicroBenchmarks.Serializers.Xml_FromStream*'
```

### MicroBenchmarks.Serializers.Xml_FromStream<LoginViewModel>.XmlSerializer_

#### 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 | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [490a2b069df755f1489170c5ba2a27ce272d1c69](https://github.com/dotnet/runtime/commit/490a2b069df755f1489170c5ba2a27ce272d1c69)
Compare | [ba8afceee83540ed1d867987483f74d4ad2cfae9](https://github.com/dotnet/runtime/commit/ba8afceee83540ed1d867987483f74d4ad2cfae9)
Diff | [Diff](https://github.com/dotnet/runtime/compare/490a2b069df755f1489170c5ba2a27ce272d1c69...ba8afceee83540ed1d867987483f74d4ad2cfae9)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Reflection.Metadata.Perf_TypeName

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

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

| 157.13 ns | 165.77 ns | 1.05 | 0.37 | 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.Reflection.Metadata.Perf_TypeName*'
```

### System.Reflection.Metadata.Perf_TypeName.ParseAndGetFullName(input: typeof(System.Int32[]))

#### 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 three benchmark sources named in the report: BinaryWriterTests.cs, Xml_FromStream.cs, and Perf.TypeName.cs. Run the listed benchmarks on Linux/arm64 and compare them with the linked baseline and compare commits. Done means identifying the cause of each reported regression and validating that the performance result is restored or the regression is explained.

Written by the indexing model from the issue text.