Inconsistant CPU loading data from Task Manager

Question

I am running Vista Home Premium 32 bit, Service pack 2 with the latest patches. My system has a dual core Intel processor. I have noticed an inconsistency in the CPU loading data from the task manager. Viewing the processes under the proces tab shows the System Idle Process is at about 80-85%. However, the CPU Usage shown at the bottom of the task manager is about 45-50%.  When I observe the system performance with the Performance Monitor (Computer management >  Reliability and performance > Monitoring tools > Performance monitor) it shows

 % Processor time = 50-55% (About 45% privileged mode and 5% user mode)

 % Idle time = 45-50%

What could be causing the inconsistency between the task manager reported system idle process and the CPU usage? Is the system idle process information displayed in the task manager accurate for multi-core processors? 

Thank you.

Answer 1

Hi,

Windows-based operating systems, such as Windows NT, Windows 2000, Windows 2003, Windows XP, and Windows Vista use the generic host process svchost.exe or Service Host process for services that run from DLLs or Dynamic Host Libraries. As the svchost.exe processes can run multiple services, there can be multiple sessions of the process running on your system at the same time-with each svchost.exe consuming different amounts of CPU resources and memory. This is the reason why svchost.exe is associated with several PC problems such as 100% CPU usage problems, memory error, and excessive power utilization.

Although svchost.exe is usually detected to be the culprit that is eating up your system’s resource, it does not cause much damage. Because, in reality, svchost.exe is just a holder process for other services running on your system. For instance, virus, spyware, adware or Trojan programs may hide behind the svchost.exe process and consume a large amount of CPU and memory resources. This is the reason why when you open the Process tab of your Task Manager, you may see the svchost.exe process creating 100% CPU usage problems on your system.

Note: To open Task Manager, press the Ctrl + Alt + Del combination keys.

If on Windows Vista system, you are unable to view the svchost.exe process listed on the Processes tab of Task Manager window, and still your system is showing high CPU usage, then perform the following steps:

1. Select the Show processes from all users button.
2. In the User Account Control dialog box that opens, select the Continue button.
3. Now, you will be able to see several svchost.exe processes running on the system and you may notice one of them consuming high CPU resources. Next, in order to find out the service that is behind the svchost.exe process and is consuming higher CPU or memory resources, you need to do the following:
4. Once you have located the svchost.exe service that is causing the problem, right-click on it, and select Go to Service(s).
5. Doing this, will open the Services tab in which some of the services will be highlighted. These highlighted services will be the ones that are associated with the problematic svchost.exe process.
6. After you have identified the services that are causing the svhost.exe process to eat up system resources, you can carefully go through them and determine the service that might be causing the problem.
7. When you have determined the suspected service, first ensure that no other services or processes rely on this service, then right-click on it and select Stop Service. You can also stop the service by opening the Services Management Console from the Control Panel.

Answer 2

I have a dual core (AMDx64) with Vista Home Premium 64 bit service Pack 2 and my numbers seem to match...~75% Idle 25%Total processor time in Perfmon, the same in Task Manager.

I don't know if the 32 vs 64 bit or Intel vs AMD is part of the difference or not.

The System Idle Time, Processor Time (and all the other parameters) in Performance Monitor can be  displayed for each processor or as a total. They are labled instance 0 and 1 and total. Are all the % you quoted for the totals?

Also try adjusting the "Update Speed" in the view tab of task manager and the "Duration" entry in the box at the bottom of the Perfmon graph. The usage numbers may be showing different due to the sampleing and averageing rates being way different between the two programs.

Still the 125% total  in Task Manager sure looks strange in your case. I don't see how Idle plus Usage (or anything else) could go over 100%.

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