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We have quite a big ASP.NET WebForms application. It runs on a dedicated physic server (96GB RAM, 16 CPU). It has Hyper-V, with a few virtual machines for IIS, MSSQL and .NET windows service for long tasks.

We are checking the application when there are no users and any load. But sometimes on page refresh, we see how IIS is hanging on for 20 secs. A profile shows that the method Process_Request takes most of this time. But the server is not loaded at all, almost zero CPU, a heap of free RAM.

What can make IIS lag this way?

Check out a screenshot with a log: Stack trace

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Iliya Garakh
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  • It could be literally thousands of things, ranging from https://stackoverflow.com/questions/3629709/i-just-discovered-why-all-asp-net-websites-are-slow-and-i-am-trying-to-work-out to https://blogs.msdn.microsoft.com/tess/2006/02/23/asp-net-performance-case-study-web-service-calls-taking-forever/ . – mjwills Mar 04 '19 at 12:10
  • How often does the issue occur? – mjwills Mar 04 '19 at 12:15
  • I can't provide any example of code, it's just impossible. It occurs once in a couple of minutes. Accidentally one query takes 20 secs instead of <1s. – Iliya Garakh Mar 04 '19 at 12:26
  • If you can't provide an example, there isn't much we can do. As I said, there are thousands of things that could be causing this. – mjwills Mar 04 '19 at 23:23
  • @mjwills, as you can see, the trace shows that Process_Request takes 10+ secs. If the reason was in our business logic we would catch it up with our log system (I mean if our code is laggy). But it looks like the problem is somewhere inside of WebForms or IIS. Like request's thread is suspended by some reason. You say there could be thousands of things, can you give at least any particular idea of such "thing"? May be it helps us find something new, because we've already checked everything, and are stuck on this bad magic. – Iliya Garakh Mar 06 '19 at 11:28

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