Runtime configuration options for compilation

This article details the settings you can use to configure .NET compilation.

Tiered compilation

• Configures whether the just-in-time (JIT) compiler uses tiered compilation. Tiered compilation transitions methods through two tiers:
  • The first tier generates code more quickly (quick JIT) or loads pre-compiled code (ReadyToRun).
  • The second tier generates optimized code in the background ("optimizing JIT").
• In .NET Core 3.0 and later, tiered compilation is enabled by default.
• In .NET Core 2.1 and 2.2, tiered compilation is disabled by default.
• For more information, see the Tiered compilation guide.

	Setting name	Values
runtimeconfig.json	System.Runtime.TieredCompilation	true - enabled false - disabled
MSBuild property	TieredCompilation	true - enabled false - disabled
Environment variable	DOTNET_TieredCompilation	1 - enabled 0 - disabled

Examples

runtimeconfig.json file:

{
   "runtimeOptions": {
      "configProperties": {
         "System.Runtime.TieredCompilation": false
      }
   }
}

runtimeconfig.template.json file:

{
   "configProperties": {
      "System.Runtime.TieredCompilation": false
   }
}

Project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TieredCompilation>false</TieredCompilation>
  </PropertyGroup>

</Project>

Quick JIT

• Configures whether the JIT compiler uses quick JIT. For methods that don't contain loops and for which pre-compiled code is not available, quick JIT compiles them more quickly but without optimizations.
• Enabling quick JIT decreases startup time but can produce code with degraded performance characteristics. For example, the code may use more stack space, allocate more memory, and run slower.
• If quick JIT is disabled but tiered compilation is enabled, only pre-compiled code participates in tiered compilation. If a method is not pre-compiled with ReadyToRun, the JIT behavior is the same as if tiered compilation were disabled.
• In .NET Core 3.0 and later, quick JIT is enabled by default.
• In .NET Core 2.1 and 2.2, quick JIT is disabled by default.

	Setting name	Values
runtimeconfig.json	System.Runtime.TieredCompilation.QuickJit	true - enabled false - disabled
MSBuild property	TieredCompilationQuickJit	true - enabled false - disabled
Environment variable	DOTNET_TC_QuickJit	1 - enabled 0 - disabled

Examples

runtimeconfig.json file:

{
   "runtimeOptions": {
      "configProperties": {
         "System.Runtime.TieredCompilation.QuickJit": false
      }
   }
}

runtimeconfig.template.json file:

{
   "configProperties": {
      "System.Runtime.TieredCompilation.QuickJit": false
   }
}

Project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TieredCompilationQuickJit>false</TieredCompilationQuickJit>
  </PropertyGroup>

</Project>

Quick JIT for loops

• Configures whether the JIT compiler uses quick JIT on methods that contain loops.
• Enabling quick JIT for loops may improve startup performance. However, long-running loops can get stuck in less-optimized code for long periods.
• If quick JIT is disabled, this setting has no effect.
• If you omit this setting, quick JIT is not used for methods that contain loops. This is equivalent to setting the value to false.

	Setting name	Values
runtimeconfig.json	System.Runtime.TieredCompilation.QuickJitForLoops	false - disabled true - enabled
MSBuild property	TieredCompilationQuickJitForLoops	false - disabled true - enabled
Environment variable	DOTNET_TC_QuickJitForLoops	0 - disabled 1 - enabled

Examples

runtimeconfig.json file:

{
   "runtimeOptions": {
      "configProperties": {
         "System.Runtime.TieredCompilation.QuickJitForLoops": false
      }
   }
}

runtimeconfig.template.json file:

{
   "configProperties": {
      "System.Runtime.TieredCompilation.QuickJitForLoops": false
   }
}

Project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TieredCompilationQuickJitForLoops>true</TieredCompilationQuickJitForLoops>
  </PropertyGroup>

</Project>

ReadyToRun

• Configures whether the .NET runtime uses pre-compiled code for images with available ReadyToRun data. Disabling this option forces the runtime to JIT-compile framework code.
• For more information, see Ready to Run.
• If you omit this setting, .NET uses ReadyToRun data when it's available. This is equivalent to setting the value to 1.

	Setting name	Values
Environment variable	DOTNET_ReadyToRun	1 - enabled 0 - disabled

Dynamic code

Set this option to false to test fallback code that you need when dynamic code isn't supported, such as in Native AOT apps, without publishing with Native AOT. The option causes RuntimeFeature.IsDynamicCodeSupported to return false.

	Setting name	Values
runtimeconfig.json	System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported	true - supported false - not supported
MSBuild property	DynamicCodeSupport	true - supported false - not supported

Example

Project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <DynamicCodeSupport>false</DynamicCodeSupport>
  </PropertyGroup>

</Project>

Profile-guided optimization

This setting enables dynamic (tiered) profile-guided optimization (PGO) in .NET 6 and later versions.

	Setting name	Values
Environment variable	DOTNET_TieredPGO	1 - enabled 0 - disabled
MSBuild property	TieredPGO	true - enabled false - disabled

Profile-guided optimization (PGO) is where the JIT compiler generates optimized code in terms of the types and code paths that are most frequently used. Dynamic PGO works hand-in-hand with tiered compilation to further optimize code based on additional instrumentation that's put in place during tier 0.

Examples

Project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TieredPGO>true</TieredPGO>
  </PropertyGroup>

</Project>