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I have two .NET 4.6.1 MVC web applications, with identical code, that are running on IIS 10.0.14393.0 on Windows Server 2016. When viewing the worker process in IIS, the memory is around 150mb for Site A but 350mb for Site B. I know the code is identical because I copied the directory for Site A to create Site B. I've checked the application pools settings for both and they're identical with 0 for both Private Memory Limit and Virtual Memory Limit as well as all other settings being identical.

This is a dev server so no one else is accessing these applications. The only actions that were performed were displaying the login page. The application was not displayed in the Worker Process section until I went to the login page. Has anyone ever experienced this type of memory discrepancy before for 2 identical sites and have any suggestions for things to review?

I've also moved the code to a different server and its memory usage is similar to Site B. I've followed the instructions at the following site to look for memory leaks but it didn't find any issues. Which would make sense because this is not necessarily a memory leak but a site using a large amount of memory initially in one instance and not in another.

https://learn.microsoft.com/en-us/iis/troubleshoot/performance-issues/troubleshooting-native-memory-leak-in-an-iis-7x-application-pool

Based upon it allocating memory vastly differently between two applications running identical code with identical requests on the same server, I would suspect this is a server setting or IIS setting somewhere that I'm missing or just a base misunderstanding of how IIS allocates memory for the worker process. Any assistance or related resources would be greatly appreciated.

I also reviewed this article but my scenario is different as the identical sites are on the same server: IIS worker process making high memory usage

Billy Rudasill
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  • Use a memory profiler or use hang dump analysis. Tons of materials over the internet for such a huge topic. – Lex Li Apr 30 '20 at 03:31
  • Thanks! This is my first foray into troubleshooting memory issues so I'll check those out. We did find if we update Site B to use the Site A app pool that the memory usage for Site B goes to 150mb. So it definitely seems like something tied to that specific app pool which is keeping memory usage low. – Billy Rudasill Apr 30 '20 at 15:15

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The issue was indeed related to a difference between Application Pool settings. In my initial comparison between Site A and Site B, I missed that Site A had Enable 32 Bit Applications set to True and Site B had Enable 32 Bit Applications set to False.

The lesson here is to double check after comparing settings. :-)

Billy Rudasill
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