[Perf] Linux/x64: 2 Regressions on 8/3/2026 7:26:34 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [79efd2de59f086171fd811d7375241616c43b890](https://github.com/dotnet/runtime/commit/79efd2de59f086171fd811d7375241616c43b890)
Compare | [c4fc2a5afc5644e10973054b1aa63c27a1584404](https://github.com/dotnet/runtime/commit/c4fc2a5afc5644e10973054b1aa63c27a1584404)
Diff | [Diff](https://github.com/dotnet/runtime/compare/79efd2de59f086171fd811d7375241616c43b890...c4fc2a5afc5644e10973054b1aa63c27a1584404)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Text.Tests.Perf_StringBuilder

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

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

| 53.40 ns | 56.67 ns | 1.06 | 0.10 | 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.Text.Tests.Perf_StringBuilder*'
```

### System.Text.Tests.Perf_StringBuilder.ToString_SingleSegment(length: 100)

#### 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 | [79efd2de59f086171fd811d7375241616c43b890](https://github.com/dotnet/runtime/commit/79efd2de59f086171fd811d7375241616c43b890)
Compare | [c4fc2a5afc5644e10973054b1aa63c27a1584404](https://github.com/dotnet/runtime/commit/c4fc2a5afc5644e10973054b1aa63c27a1584404)
Diff | [Diff](https://github.com/dotnet/runtime/compare/79efd2de59f086171fd811d7375241616c43b890...c4fc2a5afc5644e10973054b1aa63c27a1584404)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Text.Json.Tests.Perf_Booleans

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

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

| 3.94 ms | 4.20 ms | 1.07 | 0.10 | 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.Text.Json.Tests.Perf_Booleans*'
```

### System.Text.Json.Tests.Perf_Booleans.WriteBooleans(Formatted: True, SkipValidation: True)

#### 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 by reading the linked benchmark sources in src/benchmarks/micro/libraries/System.Text/Perf.StringBuilder.cs and src/benchmarks/micro/libraries/System.Text.Json/Utf8JsonWriter/Perf.Booleans.cs. Reproduce each benchmark with benchmarks_ci.py, then compare the baseline and compare commits and their performance reports. Done means identifying and resolving the cause of both reported regressions, with the benchmarks no longer showing the regression.

Written by the indexing model from the issue text.