I have six websites on IIS and its worker process memory is around 1.5 GB and its not decreasing after process completion until I run some other applications on system which required memory, then IIS Worker Process memory is decreasing with increasing of other applications memory.
Follow the below step. its works for me.
Step 1: To enable GC memory tuning, add the following setting to the Windows\Microsoft.NET\Framework\v4.0.30319\aspnet.config Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet.config
<configuration>
<!-- ... -->
<runtime>
<performanceScenario value="HighDensityWebHosting" />
<!-- ... -->
link > https://learn.microsoft.com/en-us/aspnet/whitepapers/whats-new-in-aspnet-45-and-visual-studio-2012