[Perf] Linux/x64: 13 Regressions on 8/24/2026 1:18:54 AM +00:00

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#78,742 opened on Sep 1, 2026 3 comments 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 runkind-micro untriaged wasm-aot

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Forks: 8
PR merge metrics: PR metrics pending

Description

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [efc7248c8c8a7aa7ad30a58623ee5284ce462a17](https://github.com/dotnet/runtime/commit/efc7248c8c8a7aa7ad30a58623ee5284ce462a17)
Compare | [d5d5cbcba8af2882afdda08e5b667206c7dbf09a](https://github.com/dotnet/runtime/commit/d5d5cbcba8af2882afdda08e5b667206c7dbf09a)
Diff | [Diff](https://github.com/dotnet/runtime/compare/efc7248c8c8a7aa7ad30a58623ee5284ce462a17...d5d5cbcba8af2882afdda08e5b667206c7dbf09a)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

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

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

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

| 14.35 ns | 22.69 ns | 1.58 | 0.10 | False | | |
|

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

| 15.98 ns | 23.50 ns | 1.47 | 0.10 | False | | |
|

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

| 35.82 ns | 43.43 ns | 1.21 | 0.04 | False | | |
|

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

| 145.35 ns | 156.20 ns | 1.07 | 0.03 | 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.Memory.Span*'
```

### System.Memory.Span<Byte>.ToArray(Size: 4)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Byte>.ToArray(Size: 33)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Byte>.ToArray(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Byte>.ToArray(Size: 3000)

#### 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

### Regressions in System.Memory.Span<Char>

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

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

| 14.56 ns | 22.30 ns | 1.53 | 0.08 | False | | |
|

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

| 17.80 ns | 25.39 ns | 1.43 | 0.08 | False | | |
|

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

| 68.64 ns | 76.36 ns | 1.11 | 0.11 | False | | |

![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.Memory.Span*'
```

### System.Memory.Span<Char>.ToArray(Size: 4)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Char>.ToArray(Size: 33)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Char>.ToArray(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Memory.Span<Int32>

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

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

| 14.77 ns | 22.74 ns | 1.54 | 0.07 | False | | |
|

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

| 21.01 ns | 28.26 ns | 1.34 | 0.06 | 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.Memory.Span*'
```

### System.Memory.Span<Int32>.ToArray(Size: 4)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Int32>.ToArray(Size: 33)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Tests.Perf_Enum

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

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

| 45.51 ns | 50.55 ns | 1.11 | 0.10 | False | | |
|

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

| 52.49 ns | 57.29 ns | 1.09 | 0.14 | 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.Tests.Perf_Enum*'
```

### System.Tests.Perf_Enum.GetValuesAsUnderlyingType_Generic

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_Enum.GetValuesAsUnderlyingType_NonGeneric

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Text.Tests.Perf_Encoding

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

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

| 34.21 ns | 37.88 ns | 1.11 | 0.07 | 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_Encoding*'
```

### System.Text.Tests.Perf_Encoding.GetBytes(size: 16, encName: "utf-8")

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

---

### Run Information

### Regressions in System.Memory.Memory<Byte>

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

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

| 44.13 ns | 48.22 ns | 1.09 | 0.11 | 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.Memory*'
```

### System.Memory.Memory<Byte>.ToArray(Size: 512)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

Contributor guide

No contributing guide indexed for this repository

Research direction

Start with the benchmark source at src/benchmarks/micro/libraries/System.Memory/Span.cs#L59-L60 and compare the listed baseline and compare commits. Run the documented benchmarks_ci.py command for System.Memory.Span and inspect the linked performance reports. Done means identifying the regression and confirming the affected ToArray benchmarks no longer regress under the reported Ubuntu x64 WASM AOT configuration.

Written by the indexing model from the issue text.

Assessment

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

[Perf] Linux/x64: 13 Regressions on 8/24/2026 1:18:54 AM +00:00

Description

Contributor guide

Research direction

Assessment

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