[Perf] Linux/x64: 2 Improvements on 8/7/2026 3:11:20 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [55fba988b198b5d36d3adae189b4ab1d1420cf7c](https://github.com/dotnet/runtime/commit/55fba988b198b5d36d3adae189b4ab1d1420cf7c)
Compare | [45fb46d810550207fe12a2b02dabec25f47c71ad](https://github.com/dotnet/runtime/commit/45fb46d810550207fe12a2b02dabec25f47c71ad)
Diff | [Diff](https://github.com/dotnet/runtime/compare/55fba988b198b5d36d3adae189b4ab1d1420cf7c...45fb46d810550207fe12a2b02dabec25f47c71ad)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Improvements in System.Memory.Span<Byte>

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

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

| 2.11 μs | 1.78 μs | 0.84 | 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.Memory.Span*'
```

### System.Memory.Span<Byte>.CopyTo(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 | [55fba988b198b5d36d3adae189b4ab1d1420cf7c](https://github.com/dotnet/runtime/commit/55fba988b198b5d36d3adae189b4ab1d1420cf7c)
Compare | [45fb46d810550207fe12a2b02dabec25f47c71ad](https://github.com/dotnet/runtime/commit/45fb46d810550207fe12a2b02dabec25f47c71ad)
Diff | [Diff](https://github.com/dotnet/runtime/compare/55fba988b198b5d36d3adae189b4ab1d1420cf7c...45fb46d810550207fe12a2b02dabec25f47c71ad)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Improvements in System.Collections.IterateFor<String>

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

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

| 1381.15 μs | 901.53 μs | 0.65 | 0.29 | 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.IterateFor*'
```

### System.Collections.IterateFor<String>.IList(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 benchmark commands in the issue and inspect src/benchmarks/micro/libraries/System.Memory/Span.cs lines 44-45 and src/benchmarks/micro/libraries/System.Collections/Iterate/IterateFor.cs lines 90-92. Compare the reported results with the linked history and reports; done means the performance change is reproduced and its cause or required follow-up is established.

Written by the indexing model from the issue text.