[Perf] Windows/x86: 4 Improvements on 8/10/2026 5:38:55 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [ab094c18ba7f4a96d145afd8b34f965c5c3ef31d](https://github.com/dotnet/runtime/commit/ab094c18ba7f4a96d145afd8b34f965c5c3ef31d)
Compare | [c12540eb53044276c55a86c3a834c662eff2872f](https://github.com/dotnet/runtime/commit/c12540eb53044276c55a86c3a834c662eff2872f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/ab094c18ba7f4a96d145afd8b34f965c5c3ef31d...c12540eb53044276c55a86c3a834c662eff2872f)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Formats.Tar.Tests.Perf_TarWriter

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

• [V7TarEntry_WriteEntry - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

| 379.72 ns | 310.29 ns | 0.82 | 0.07 | False | | |
|

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

| 2.17 μs | 1.78 μs | 0.82 | 0.01 | False | | |
|

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

| 390.63 ns | 336.37 ns | 0.86 | 0.10 | False | | |
|

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

| 361.23 ns | 320.44 ns | 0.89 | 0.08 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Formats.Tar.Tests.Perf_TarWriter*'
```

### System.Formats.Tar.Tests.Perf_TarWriter.V7TarEntry_WriteEntry

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Formats.Tar.Tests.Perf_TarWriter.PaxTarEntry_WriteEntry

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Formats.Tar.Tests.Perf_TarWriter.GnuTarEntry_WriteEntry

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Formats.Tar.Tests.Perf_TarWriter.UstarTarEntry_WriteEntry

#### 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 source at performance/src/benchmarks/micro/libraries/System.Formats.Tar/Perf.Tar.cs lines 45-51, 61-67, 77-83, and 93-99, then run the provided benchmarks_ci.py command. Compare the linked baseline and test reports to determine whether the Windows/x86 improvement has an actionable cause; completion requires a validated investigation or an agreed runtime change with benchmark evidence.

Written by the indexing model from the issue text.