Question

I am encountering an issue with my asp.net c# web application where the server is hitting very high cpu useage eg. 80%+ on w3wp process.

This has only happened recently after I made numerous changes to my application. I am fairly sure that it may be one of the changes that I have made is causing this issue with high cpu useage on the iis 7 web server.

Is it possible to analyze the process and find what exactly is causing this high useage? Or what is the mechanism for debugging such an issue.

Answer 1

ASP.NET Case Study: High CPU in GC - Large objects and high allocation rates:

A high CPU issue is generally one of 3 things

An infinite loop

Too much load (i.e. too many requests doing lots of small things, so no one single thing is a culprit)

Too much churning in the Garbage Collector.

Try monitoring the % Time in GC counter and the .NET CLR Memory / # Gen 0 Collections, # Gen 1 Collections and # Gen 2 Collections.

Are you calling GC.Collect() anywhere in your code?

The problem you are describing also sounds symptomatic of High CPU in .NET app using a static Generic.Dictionary, caused by multiple threads hitting the dictionary. If that s the problem:

To resolve this timing issue you should take special care to synchronize (lock) around access to the dictionary if there is a possibility that you may have multiple writers working at the same time or if there is a possibility that you write while someone else is reading/enumerating through the same dictionary.

Related: ASP.NET Performance Monitoring, and When to Alert Administrators

Answer 2

The quickest way is to enable Page Tracing. This will tell you exactly how long the page took to generate, and in which methods the server spent most of it s time. This should highlight any particularly slow-running methods, allowing you to focus your troubleshooting on the problematic sections.

Simply add the following to any pages you suspect of being troublesome:

<%@ Page Trace="true" %>

Now, when you navigate to that page in your browser, you will get a detailed trace at the bottom of it.

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