[Perf] Linux/x64: 4 Regressions on 6/29/2026 9:51:56 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [0d3df07c6048d8cbe4f544227462cae62040e587](https://github.com/dotnet/runtime/commit/0d3df07c6048d8cbe4f544227462cae62040e587)
Compare | [93ec56ee6c38a470c6fed16b59d3f130587b1a06](https://github.com/dotnet/runtime/commit/93ec56ee6c38a470c6fed16b59d3f130587b1a06)
Diff | [Diff](https://github.com/dotnet/runtime/compare/0d3df07c6048d8cbe4f544227462cae62040e587...93ec56ee6c38a470c6fed16b59d3f130587b1a06)
Configs | CompilationMode:tiered, LLVM:false, MonoAOT:false, MonoInterpreter:false, RunKind:micro_mono

### Regressions 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]()

| 4.03 μs | 5.05 μs | 1.25 | 0.00 | False | | |
|

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

| 4.17 μs | 5.22 μs | 1.25 | 0.00 | False | | |
|

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

| 4.22 μs | 5.16 μs | 1.22 | 0.00 | False | | |
|

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

| 11.59 μs | 13.07 μs | 1.13 | 0.00 | False | | |

![graph]()
![graph]()
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![graph]()
[Test Report]()

### Repro
General Docs link: https://github.com/dotnet/performance/blob/main/docs/benchmarking-workflow-dotnet-runtime.md

Repro Steps

#### Prerequisites (Build files either built locally or downloaded from payload above)
- Libraries build extracted to `runtime/artifacts` or build instructions: [Libraries README](https://github.com/dotnet/runtime/blob/main/docs/workflow/building/libraries/README.md) args: `-subset libs+libs.tests -rc release -configuration Release -arch $RunArch -framework net8.0`
- CoreCLR product build extracted to `runtime/artifacts/bin/coreclr/$RunOS.$RunArch.Release`, build instructions: [CoreCLR README](https://github.com/dotnet/runtime/blob/main/docs/workflow/building/coreclr/README.md) args: `-subset clr+libs -rc release -configuration Release -arch $RunArch -framework net8.0`
- Mono Runtime build extracted to `runtime/artifacts/bin/mono/$RunOS.$RunArch.Release`, build instructions: [MONO README](https://github.com/dotnet/runtime/blob/main/docs/workflow/building/mono/README.md) args: `-arch $RunArch -os $RunOS -s mono+libs+host+packs -c Release `
- Dotnet SDK installed for dotnet commands
- Running commands from the runtime folder

Linux
```cmd
# Set $RunDir to the runtime directory
RunDir=`pwd`

# Set the OS, arch, and OSId
RunOS='linux'
RunOSId='linux'
RunArch='x64'

# Create mono dotnet
mkdir -p $RunDir/artifacts/dotnet-mono
$RunDir/build.sh -subset libs.pretest -configuration release -ci -arch $RunArch -testscope innerloop /p:RuntimeArtifactsPath=$RunDir/artifacts/bin/mono/$RunOS.$RunArch.Release /p:RuntimeFlavor=mono
cp $RunDir/artifacts/bin/runtime/net8.0-$RunOS-Release-$RunArch/* $RunDir/artifacts/bin/testhost/net8.0-$RunOS-Release-$RunArch/shared/Microsoft.NETCore.App/8.0.0 -rf
cp $RunDir/artifacts/bin/testhost/net8.0-$RunOS-Release-$RunArch/* $RunDir/artifacts/dotnet-mono -r
cp $RunDir/artifacts/bin/coreclr/$RunOS.$RunArch.Release/corerun $RunDir/artifacts/dotnet-mono/shared/Microsoft.NETCore.App/8.0.0/corerun

# Create Core Root
$RunDir/src/tests/build.sh release $RunArch generatelayoutonly /p:LibrariesConfiguration=Release

# Clone performance
git clone --branch main --depth 1 --quiet https://github.com/dotnet/performance.git $RunDir/performance

# One line run:
python3 $RunDir/performance/scripts/benchmarks_ci.py --csproj $RunDir/performance/src/benchmarks/micro/MicroBenchmarks.csproj --incremental no --architecture $RunArch -f net8.0 --filter 'System.Formats.Tar.Tests.Perf_TarWriter*' --bdn-artifacts $RunDir/artifacts/BenchmarkDotNet.Artifacts --bdn-arguments="--anyCategories Libraries Runtime --category-exclusion-filter NoInterpreter NoMono --logBuildOutput --generateBinLog --corerun $RunDir/artifacts/dotnet-mono/shared/Microsoft.NETCore.App/8.0.0/corerun"

# Individual Commands:
# Restore
dotnet restore $RunDir/performance/src/benchmarks/micro/MicroBenchmarks.csproj --packages $RunDir/performance/artifacts/packages /p:UseSharedCompilation=false /p:BuildInParallel=false /m:1

# Build
dotnet build $RunDir/performance/src/benchmarks/micro/MicroBenchmarks.csproj --configuration Release --framework net8.0 --no-restore /p:NuGetPackageRoot=$RunDir/performance/artifacts/packages /p:UseSharedCompilation=false /p:BuildInParallel=false /m:1

# Run
dotnet run --project $RunDir/performance/src/benchmarks/micro/MicroBenchmarks.csproj --configuration Release --framework net8.0 --no-restore --no-build -- --filter 'System.Formats.Tar.Tests.Perf_TarWriter*' --anyCategories Libraries Runtime " --category-exclusion-filter NoInterpreter NoMono --logBuildOutput --generateBinLog --corerun $RunDir/artifacts/dotnet-mono/shared/Microsoft.NETCore.App/8.0.0/corerun --artifacts $RunDir/artifacts/BenchmarkDotNet.Artifacts --packages $RunDir/performance/artifacts/packages
```

Windows
```cmd
# Set $RunDir to the runtime directory
$RunDir="FullPathHere"

# Set the OS, arch, and OSId
RunOS='windows'
RunOSId='win'
RunArch='x64'

# Create mono dotnet
mkdir -p $RunDir/artifacts/dotnet-mono
$RunDir/build.sh -subset libs.pretest -configuration release -ci -arch $RunArch -testscope innerloop /p:RuntimeArtifactsPath=$RunDir\artifacts\bin\mono\$RunOS.$RunArch.Release /p:RuntimeFlavor=mono
xcopy $RunDir\artifacts\bin\runtime\net8.0-$RunOS-Release-$RunArch\ $RunDir\artifacts\bin\testhost\net8.0-$RunOS-Release-$RunArch\shared\Microsoft.NETCore.App\8.0.0\ /e /y
xcopy $RunDir\artifacts\bin\testhost\net8.0-$RunOS-Release-$RunArch\ $RunDir\artifacts\dotnet-mono\ /e /y
xcopy $RunDir\artifacts\bin\coreclr\$RunOS.$RunArch.Release\corerun $RunDir\artifacts\dotnet-mono\shared\Microsoft.NETCore.App\8.0.0\corerun /y

# Create Core Root
$RunDir\src\tests\build.cmd release $RunArch generatelayoutonly /p:LibrariesConfiguration=Release

# Clone performance
git clone --branch main --depth 1 --quiet https://github.com/dotnet/performance.git $RunDir\performance

# One line run:
python3 $RunDir\performance\scripts\benchmarks_ci.py --csproj $RunDir\performance\src\benchmarks\micro\MicroBenchmarks.csproj --incremental no --architecture $RunArch -f net8.0 --filter 'System.Formats.Tar.Tests.Perf_TarWriter*' --bdn-artifacts $RunDir\artifacts\BenchmarkDotNet.Artifacts --bdn-arguments="--anyCategories Libraries Runtime --category-exclusion-filter NoInterpreter NoMono --logBuildOutput --generateBinLog --corerun $RunDir\artifacts\dotnet-mono\shared\Microsoft.NETCore.App\8.0.0\corerun.exe"

# Individual Commands:
# Restore
dotnet restore $RunDir\performance\src\benchmarks\micro\MicroBenchmarks.csproj --packages $RunDir\performance\artifacts\packages /p:UseSharedCompilation=false /p:BuildInParallel=false /m:1

# Build
dotnet build $RunDir\performance\src\benchmarks\micro\MicroBenchmarks.csproj --configuration Release --framework net8.0 --no-restore /p:NuGetPackageRoot=$RunDir\performance\artifacts\packages /p:UseSharedCompilation=false /p:BuildInParallel=false /m:1

# Run
dotnet run --project $RunDir\performance\src\benchmarks\micro\MicroBenchmarks.csproj --configuration Release --framework net8.0 --no-restore --no-build -- --filter 'System.Formats.Tar.Tests.Perf_TarWriter*' --anyCategories Libraries Runtime " --category-exclusion-filter NoInterpreter NoMono --logBuildOutput --generateBinLog --corerun $RunDir\artifacts\dotnet-mono\shared\Microsoft.NETCore.App\8.0.0\corerun.exe --artifacts $RunDir\artifacts\BenchmarkDotNet.Artifacts --packages $RunDir\performance\artifacts\packages
```

### System.Formats.Tar.Tests.Perf_TarWriter.V7TarEntry_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

### System.Formats.Tar.Tests.Perf_TarWriter.PaxTarEntry_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 comparison between commits 0d3df07c6048d8cbe4f544227462cae62040e587 and 93ec56ee6c38a470c6fed16b59d3f130587b1a06, then inspect performance/src/benchmarks/micro/libraries/System.Formats.Tar/Perf.Tar.cs at the listed benchmark entries. Follow the benchmarking workflow documentation and run the Perf_TarWriter filter; done means the regression is explained and the affected benchmarks no longer regress.

Written by the indexing model from the issue text.