ASP.NET: High CPU usage under no load

Question

I´m facing a huge problem since a couple weeks. I´ve an asp.net application hosted under IIS7 (W2008 SP1), and every a couple hours it starts consuming near 50% of the CPU when

Answer 1

Is this possibly being caused by a cache issue? For example, do you have a cached dataset set to automatically re-load from the DB when it expires?

We had this situation once. We had a large dataset that we wanted to be always available. The data didn't change that often, so we set it in the cache with a 1 hour expiration, and then in our global.asax, we handled the removal (as described here without paying attention tot e warning described in the link. We re-loaded the dataset to the cache after the hour had passed and this caused high cpu usage and high db usage every hour.

edit - added

Needless to say, we saw this quickly and learned from our mistake.

Answer 2

In windbg, issue:

~*e !clrstack

This will dump all of the managed thread stacks and should give you an idea of what is happening in that process.

Also try a !runaway, which will show you how much time each thread has been running. Focus on the stacks of the top threads which are the ones that have been running longest.