[Perf] Linux/arm64: 4 Regressions on 6/26/2026 6:28:17 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55](https://github.com/dotnet/runtime/commit/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55)
Compare | [207ffd155f96b38be1749584b99f3ac0a505218c](https://github.com/dotnet/runtime/commit/207ffd155f96b38be1749584b99f3ac0a505218c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55...207ffd155f96b38be1749584b99f3ac0a505218c)
Configs | CompilationMode:tiered, R2RType:r2r_interpreter, RunKind:micro

### Regressions in System.Collections.ContainsTrue<Int32>

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

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

| 5.78 μs | 6.61 μs | 1.14 | 0.14 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.ContainsTrue*'
```

### System.Collections.ContainsTrue<Int32>.HashSet(Size: 512)

#### 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 | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55](https://github.com/dotnet/runtime/commit/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55)
Compare | [207ffd155f96b38be1749584b99f3ac0a505218c](https://github.com/dotnet/runtime/commit/207ffd155f96b38be1749584b99f3ac0a505218c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55...207ffd155f96b38be1749584b99f3ac0a505218c)
Configs | CompilationMode:tiered, R2RType:r2r_interpreter, RunKind:micro

### Regressions in Benchstone.BenchI.BenchE

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

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

| 526.32 ms | 666.97 ms | 1.27 | 0.13 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'Benchstone.BenchI.BenchE*'
```

### Benchstone.BenchI.BenchE.Test

#### 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 | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55](https://github.com/dotnet/runtime/commit/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55)
Compare | [207ffd155f96b38be1749584b99f3ac0a505218c](https://github.com/dotnet/runtime/commit/207ffd155f96b38be1749584b99f3ac0a505218c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55...207ffd155f96b38be1749584b99f3ac0a505218c)
Configs | CompilationMode:tiered, R2RType:r2r_interpreter, RunKind:micro

### Regressions in Benchmark.GetChildKeysTests

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

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

| 17.93 ms | 25.29 ms | 1.41 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'Benchmark.GetChildKeysTests*'
```

### Benchmark.GetChildKeysTests.AddChainedConfigurationEmpty

#### 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 | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55](https://github.com/dotnet/runtime/commit/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55)
Compare | [207ffd155f96b38be1749584b99f3ac0a505218c](https://github.com/dotnet/runtime/commit/207ffd155f96b38be1749584b99f3ac0a505218c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22c1ced1d71c05e96f9cca3c2d6171ba9e5f0a55...207ffd155f96b38be1749584b99f3ac0a505218c)
Configs | CompilationMode:tiered, R2RType:r2r_interpreter, RunKind:micro

### Regressions in System.Collections.HashSetContains<Int32>

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

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

| 5.98 μs | 6.86 μs | 1.15 | 0.12 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.HashSetContains*'
```

### System.Collections.HashSetContains<Int32>.ContainsTrue(Size: 512)

#### 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 listed benchmark sources: ContainsTrue.cs, BenchE.cs, GetChildKeysTests.cs, and HashSetContains.cs. Run the provided benchmarks_ci.py filters, then compare the reported ARM64 AzureLinux results with the linked baseline and test commits. Done means the cause and disposition of all four performance regressions are established and the regressions are resolved or explained.

Written by the indexing model from the issue text.