Runtime configuration options for compilation

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

Note

.NET 6 standardizes on the prefix DOTNET_ instead of COMPlus_ for environment variables that configure .NET run-time behavior. However, the COMPlus_ prefix will continue to work. If you're using a previous version of the .NET runtime, you should still use the COMPlus_ prefix for environment variables.

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	COMPlus_TieredCompilation or 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	COMPlus_TC_QuickJit or 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	COMPlus_TC_QuickJitForLoops or 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 Core 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	COMPlus_ReadyToRun or DOTNET_ReadyToRun	1 - enabled 0 - disabled

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>