[release/6.0] Environment variable should override property for gcServer.

[github-actions]

Backport of #61950 to release/6.0

/cc @AaronRobinsonMSFT

Customer Impact

This is a regression from .NET 5 to .NET 6 (when we consolidated complus_ into dotnet_ environment variable naming). The change in behavior has been observed by multiple customers.

The ASP.NET Core project default settings define the GC to operate in Server mode. However, Some customers prefer Workstation. The recommended approach to address this is setting DOTNET_gcServer=0, which will override the default configuration property. Without this change the only workaround is to edit the project runtimeconfig.json file via a template or set an MSBuild property.

Testing

A test was added for the impacted scenario.

Risk

Low. The change is permitting a niche scenario for the overriding of configuration properties. The only known consumer of this change is the tested GC scenario.

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[ghost]

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Issue Details

---

Backport of #61950 to release/6.0

/cc @AaronRobinsonMSFT

Customer Impact

The ASP.NET Core project default settings define the GC to operate in Server mode. However, Some customers prefer Workstation. The recommended approach to address this is setting DOTNET_gcServer=0, which will override the default configuration property. Without this change the only workaround is to edit the project runtimeconfig.json file via a template or set an MSBuild property.

Testing

A test was added for the impacted scenario.

Risk

Low. The change is permitting a niche scenario for the overriding of configuration properties. The only known consumer of this change is the tested GC scenario.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-GC-coreclr
Milestone:	-

[AaronRobinsonMSFT]

/cc @mangod9 @cshung

[mangod9]

since this is a regression should consider for 6.0.x

[jeffschwMSFT]

Approved. We should take for consideration for 6.0.x

[mangod9]

Some clarifications on this:

1. This is a regression from .net 5.0, where-in if you try to override the gcServer setting via environment variable (to disable it, since that is the default) it doesnt take effect
2. Couple of external customers have hit this: Garbage collection method is not manageable by environment variables in .net 6 #61674 and Different Heap behavior between 5.0 and 6.0. Maybe memory leak? #62182
3. Please note that upgrading to .net 6 seems to show a memory utilization regression since the app switches from wks to svr.