How to disable Server GC in ASP.NET Framework App running on Azure App Service

Question

I'm doing some high density hosting of ASP.NET MVC 5 / WCF apps on Azure App Service and the idle apps are using 600~1000MB of memory each which is quite a lot, given that a memory dump reveals that the GC heap is only about ~40MB full. I suspect this is due to server GC so i tried disabling it by following https://docs.microsoft.com/en-us/dotnet/framework/configure-apps/file-schema/runtime/gcserver-element and adding

<gcServer enabled="false" />

to my web.config, but this does not appear to have any effect as

GCSettings.IsServerGC

is still returning true. What am i missing here?

EDIT:

Using normal IIS it can be done using https://weblogs.asp.net/owscott/setting-an-aspnet-config-file-per-application-pool but in Azure App Service, you lack the permissions to do this.

Answer 1

Ok, first of all, it seems like you might have to manually debug the memory usage of components using GC.Collect(): https://docs.microsoft.com/en-us/dotnet/api/system.gc.collect?view=netcore-3.1

This way you might be able to pinpoint a specific part of the code that either causes a memory leak due to bad garbage collection, or parts that are using certain third-party libraries.

Once you are done with this quite tedious part, then depending on what you think is causing the problem, you should consider either using a manual disposal of the code block utilizing (using var item = new NameOfClass()) or even trying ti implement IDispose on the classes that are causing it: https://docs.microsoft.com/en-us/dotnet/standard/garbage-collection/implementing-dispose.