[Perf] Linux/x64: 17 Regressions on 8/19/2026 2:54:37 PM +00:00

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#78,560 opened on Aug 27, 2026 1 comment 0 reactions 0 assignees View on GitHub

aot-true arch-wasm arch-x64 branch-refs/heads/main compilationmode-wasm kind-micro Look Again os-linux perf-regression PGO runkind-micro untriaged wasm-aot

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Forks: 8
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Description

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [029a98f26a9506810140781e88ccb8e45de1cc79](https://github.com/dotnet/runtime/commit/029a98f26a9506810140781e88ccb8e45de1cc79)
Compare | [361539de30ffe5c5ccb7cbdfa230747411ec7faf](https://github.com/dotnet/runtime/commit/361539de30ffe5c5ccb7cbdfa230747411ec7faf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/029a98f26a9506810140781e88ccb8e45de1cc79...361539de30ffe5c5ccb7cbdfa230747411ec7faf)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Collections.CtorGivenSize<String>

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

[OrderedDictionary - Duration of single invocation]()
[ADX - Test Multi Config Graph]()

| 796.32 ns | 958.12 ns | 1.20 | 0.21 | False | | |
|

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

| 192.51 ns | 211.79 ns | 1.10 | 0.03 | False | | |
|

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

| 94.38 ns | 100.76 ns | 1.07 | 0.07 | False | | |
|

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

| 96.13 ns | 102.62 ns | 1.07 | 0.07 | False | | |

![graph]()
![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.Collections.CtorGivenSize*'
```

### System.Collections.CtorGivenSize<String>.OrderedDictionary(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.CtorGivenSize<String>.SortedList(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.CtorGivenSize<String>.Stack(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.CtorGivenSize<String>.Queue(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 | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [1f22605f08368b251c9ff73b935a8d7c1df4d174](https://github.com/dotnet/runtime/commit/1f22605f08368b251c9ff73b935a8d7c1df4d174)
Compare | [cb8ddc8cac0182e932903d921bd09300be7ae2a6](https://github.com/dotnet/runtime/commit/cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Diff | [Diff](https://github.com/dotnet/runtime/compare/1f22605f08368b251c9ff73b935a8d7c1df4d174...cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

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

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

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

| 38.92 μs | 41.43 μs | 1.06 | 0.07 | False | | |
|

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

| 6.82 μs | 7.24 μs | 1.06 | 0.09 | False | | |

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

### System.Linq.Tests.Perf_Enumerable.Concat_TenTimes(input: IEnumerable)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Linq.Tests.Perf_Enumerable.Concat_Once(input: IEnumerable)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in PerfLabTests.CastingPerf2.CastingPerf

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

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

| 351.43 μs | 379.53 μs | 1.08 | 0.02 | False | | |
|

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

| 454.14 μs | 487.55 μs | 1.07 | 0.02 | False | | |

![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 'PerfLabTests.CastingPerf2.CastingPerf*'
```

### PerfLabTests.CastingPerf2.CastingPerf.ObjInt

#### ETL Files

#### Histogram

#### JIT Disasms

### PerfLabTests.CastingPerf2.CastingPerf.ObjObjrefValueType

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [1f22605f08368b251c9ff73b935a8d7c1df4d174](https://github.com/dotnet/runtime/commit/1f22605f08368b251c9ff73b935a8d7c1df4d174)
Compare | [361539de30ffe5c5ccb7cbdfa230747411ec7faf](https://github.com/dotnet/runtime/commit/361539de30ffe5c5ccb7cbdfa230747411ec7faf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/1f22605f08368b251c9ff73b935a8d7c1df4d174...361539de30ffe5c5ccb7cbdfa230747411ec7faf)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

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

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

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

| 8.36 ns | 9.50 ns | 1.14 | 0.15 | 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.Collections.CtorDefaultSize*'
```

### System.Collections.CtorDefaultSize<Int32>.ConcurrentStack

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [029a98f26a9506810140781e88ccb8e45de1cc79](https://github.com/dotnet/runtime/commit/029a98f26a9506810140781e88ccb8e45de1cc79)
Compare | [cb8ddc8cac0182e932903d921bd09300be7ae2a6](https://github.com/dotnet/runtime/commit/cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Diff | [Diff](https://github.com/dotnet/runtime/compare/029a98f26a9506810140781e88ccb8e45de1cc79...cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Threading.Tests.Perf_CancellationToken

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

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

| 51.53 ns | 54.54 ns | 1.06 | 0.30 | 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.Threading.Tests.Perf_CancellationToken*'
```

### System.Threading.Tests.Perf_CancellationToken.CreateManyRegisterDispose

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Linq.Tests.Perf_ImmutableArrayExtensions

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]()

| 1.64 μs | 2.30 μs | 1.40 | 0.09 | 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_ImmutableArrayExtensions*'
```

### System.Linq.Tests.Perf_ImmutableArrayExtensions.SequenceEqual(input: IEnumerable)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in XmlDocumentTests.XmlNodeListTests.Perf_XmlNodeList

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

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

| 255.56 ns | 306.47 ns | 1.20 | 0.16 | 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 'XmlDocumentTests.XmlNodeListTests.Perf_XmlNodeList*'
```

### XmlDocumentTests.XmlNodeListTests.Perf_XmlNodeList.Enumerator

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [1f22605f08368b251c9ff73b935a8d7c1df4d174](https://github.com/dotnet/runtime/commit/1f22605f08368b251c9ff73b935a8d7c1df4d174)
Compare | [361539de30ffe5c5ccb7cbdfa230747411ec7faf](https://github.com/dotnet/runtime/commit/361539de30ffe5c5ccb7cbdfa230747411ec7faf)
Diff | [Diff](https://github.com/dotnet/runtime/compare/1f22605f08368b251c9ff73b935a8d7c1df4d174...361539de30ffe5c5ccb7cbdfa230747411ec7faf)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Tests.Perf_Random

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

[Next_long_long_unseeded - Duration of single invocation]()
[ADX - Test Multi Config Graph]()

| 17.26 ns | 19.66 ns | 1.14 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Tests.Perf_Random*'
```

### System.Tests.Perf_Random.Next_long_long_unseeded

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [029a98f26a9506810140781e88ccb8e45de1cc79](https://github.com/dotnet/runtime/commit/029a98f26a9506810140781e88ccb8e45de1cc79)
Compare | [cb8ddc8cac0182e932903d921bd09300be7ae2a6](https://github.com/dotnet/runtime/commit/cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Diff | [Diff](https://github.com/dotnet/runtime/compare/029a98f26a9506810140781e88ccb8e45de1cc79...cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Collections.Tests.Add_Remove_SteadyState<String>

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

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

| 80.98 ns | 86.27 ns | 1.07 | 0.09 | 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.Collections.Tests.Add_Remove_SteadyState*'
```

### System.Collections.Tests.Add_Remove_SteadyState<String>.ConcurrentBag(Count: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Xml.Linq.Perf_XDocument

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

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

| 8.20 ns | 10.21 ns | 1.25 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Xml.Linq.Perf_XDocument*'
```

### System.Xml.Linq.Perf_XDocument.Create

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Tests.Perf_Object

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

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

| 7.48 ns | 9.50 ns | 1.27 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Tests.Perf_Object*'
```

### System.Tests.Perf_Object.ctor

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [029a98f26a9506810140781e88ccb8e45de1cc79](https://github.com/dotnet/runtime/commit/029a98f26a9506810140781e88ccb8e45de1cc79)
Compare | [cb8ddc8cac0182e932903d921bd09300be7ae2a6](https://github.com/dotnet/runtime/commit/cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Diff | [Diff](https://github.com/dotnet/runtime/compare/029a98f26a9506810140781e88ccb8e45de1cc79...cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

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

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

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

| 18.65 μs | 22.39 μs | 1.20 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.CreateAddAndClear*'
```

### System.Collections.CreateAddAndClear<Int32>.ImmutableQueue(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

Contributor guide

No contributing guide indexed for this repository

Research direction

Start with the linked regression reports and the benchmark sources in performance/src/benchmarks/micro/libraries/System.Collections/Create/CtorGivenSize.cs and src/benchmarks/micro/libraries/System.Linq/Perf.Enumerable.cs. Run the provided benchmarks_ci.py command, compare the listed baseline and test commits, and inspect the profiling and test reports. Done means reproducing the regression, identifying its cause, and documenting the result or corrective path.

Written by the indexing model from the issue text.

Assessment

Tech stack: python, wasm
Domain: performance, testing
Issue type: Bug
Difficulty: 4/5
Estimated time: 3-5 days
Activity status: Active
Clarity: Needs clarification
Newbie friendliness: 35/100

[Perf] Linux/x64: 17 Regressions on 8/19/2026 2:54:37 PM +00:00

Description

Contributor guide

Research direction

Assessment

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