[Perf] Linux/x64: 3 Regressions on 8/14/2026 7:15:06 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [691fd960eb500743b4be71373b11b2263bdbc318](https://github.com/dotnet/runtime/commit/691fd960eb500743b4be71373b11b2263bdbc318)
Compare | [c99188c2f97b94c8b086cc9b87516b6d710ec4ff](https://github.com/dotnet/runtime/commit/c99188c2f97b94c8b086cc9b87516b6d710ec4ff)
Diff | [Diff](https://github.com/dotnet/runtime/compare/691fd960eb500743b4be71373b11b2263bdbc318...c99188c2f97b94c8b086cc9b87516b6d710ec4ff)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

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

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

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

| 870.82 μs | 1808.06 μs | 2.08 | 0.30 | False | | |
|

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

| 3.72 μs | 6.08 μs | 1.64 | 0.28 | 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.Collections.CtorFromCollection*'
```

### System.Collections.CtorFromCollection<String>.ImmutableList(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.CtorFromCollection<String>.List(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 | [691fd960eb500743b4be71373b11b2263bdbc318](https://github.com/dotnet/runtime/commit/691fd960eb500743b4be71373b11b2263bdbc318)
Compare | [c99188c2f97b94c8b086cc9b87516b6d710ec4ff](https://github.com/dotnet/runtime/commit/c99188c2f97b94c8b086cc9b87516b6d710ec4ff)
Diff | [Diff](https://github.com/dotnet/runtime/compare/691fd960eb500743b4be71373b11b2263bdbc318...c99188c2f97b94c8b086cc9b87516b6d710ec4ff)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.Buffers.Tests.ReadOnlySequenceTests<Char>

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

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

| 2.54 μs | 3.46 μs | 1.36 | 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.Buffers.Tests.ReadOnlySequenceTests*'
```

### System.Buffers.Tests.ReadOnlySequenceTests<Char>.IterateForEachMemory

#### 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.Collections/Create/CtorFromCollection.cs#L42-L43 and #L93-L94, and src/benchmarks/micro/libraries/System.Buffers/ReadOnlySequenceTests.cs#L95-L96. Reproduce the named filters with scripts/benchmarks_ci.py, then compare the linked baseline, test, and regression reports. Done means the reported Linux/x64 WebAssembly slowdowns are understood and the affected benchmarks no longer show the regression.

Written by the indexing model from the issue text.