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COMPLUS_LoaderOptimization Environment Variable

.NET Framework 4.5

An environment variable that sets the default loader optimization policy of an executable application.

COMPLUS_LoaderOptimization = 1

A typical application loads several assemblies into an application domain before the code they contain can be executed.

The way the assembly is loaded determines whether its just-in-time (JIT) compiled code can be shared by multiple application domains in the process.

  • If an assembly is loaded domain-neutral, all application domains that share the same security grant set can share the same JIT-compiled code. This reduces the memory required by the application.

  • If an assembly is not loaded domain-neutral, it must be JIT-compiled in every application domain in which it is loaded and the loader must not share internal resources across application domains.

When set to 1, the COMPLUS_LoaderOptimization environment flag forces the runtime host to load all assemblies in non-domain-neutral way known as SingleDomain. SingleDomain loads no assemblies as domain-neutral, except Mscorlib, which is always loaded domain-neutral. This setting is called single domain because it is commonly used when the host is running only a single application in the process.

Caution note Caution

The COMPLUS_LoaderOptimization environment flag was designed to be used in diagnostic and test scenarios. Having the flag turned on can cause severe slow-down and increase in memory usage.

To force all assemblies not to be loaded as domain-neutral for the IISADMIN service can be achieved by appending COMPLUS_LoaderOptimization=1 to the Environment’s Multi-String Value in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\IISADMIN key.

Name = Environment
Value (to append) = COMPLUS_LoaderOptimization=1
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