High CPU usage in system running nothing!!!

Question

I have a Windows Server 2008 Enterprise SP2
with Coldfusion 9.01 Standard Developer edition
and MS-SQL 2008 Developer database server.
I  use it mostly for testing and development. The system was working just  fine, but suddenly it started timing out queries, slowing down etc.
Even  when nothing (no application, no schedule task, no sites etc) runs in  the system I noticed that it uses 25% - 40% of system CPU.for various  period of times. Sometimes for some minutes, sometimes for many hours or  days. After this period the CPU falls to 0%-1% again and the system  works fine. After some minutes or hours the CPU goes again to 25%-40%  for no reason.
When I disabled the service "ColdFusion Application Server" then the CPU goes to 0%-1% and the system works fine permanently.
I say it again, in the system there is no site, no schedule task, no datasource.
In  the past all I had in the system was a group of Scheduled tasks. So I  deleted all scheduled tasks, I even deleted a datasource to a database I  had. So now there is no CF code running in the system. So then why the  service "ColdFusion Application Server" uses 25% - 40% of CPU resources  ????
Any ideas ?????
Anastassios

Answer 1

Yes, Anastassios, it's not as unusual as you think.
I would recommend that you look at the CF runtime (or JRun) logs. If on CF Standard or Enterprise Server, look in \runtime\logs. If running Enterprise Multiserver, look in \logs. In either case, look for the most recently written "out" log (or around the time of the problem). I suspect you're having outofmemory errors (look for that string, specifically, no spaces).
Now, don't assume that if you get them that it means you need to "add more heap". In fact, you may be better suited by using less. The question depends on the error you get. If it says "heap", then perhaps yes you need more heap (but maybe instead something us holding heap longer than it should--yes, even when no requests are running, like sessions, query caches, application scope, etc.)
But the outofmemory error may say something else, like "unable to create new native thread", or "swap space", or "permgen", and so on. These do NOT mean you need to add more heap, and may mean you'd be served well by lowering it.
There are far too many permutations to elaborate. I started a series of entries on the subject:
CF911: Lies, damned lies, and when memory problems not be at all what they seem, Part 1
http://www.carehart.org/blog/client/index.cfm/2010/11/3/when_memory_problems_arent_what_th ey_seem_part_1
I never finished it, but you may get value from what is there to start it out.
I will say that if you are still stumped and need help solving this, this sort of CF server troubleshooting is what I do for a living and I'd be happy to help. I can often solve such problems in less than an hour or two. More at www.carehart.org/consulting/. In any case, I hope the above is enough to get you started on your own.
/charlie arehart
[email protected]
Providing fast, remote, on-demand troubleshooting services for CF (and CFBuilder)
More at http://www.carehart.org/consulting