How doesAPM measure SQL Process % CPU on a multi-core server?

FormerMember

When i run the counter for Process(sqlservr)\% Processor Time in permon on my SQL server, it agrregates the process across all cores.  So if I have a 4 core CPU and SQL process is running 50% on each core, then value of the counter will be 200% while Processor(_Total)\% Processor Time would be 50%.  How does APM measure the value of the % CPU for the SQL Process?  I've never seen it go above 100% on my 8 core server.

aLTeReGo

I'm not 100% sure how Microsoft handles representing this information for multiple cores but APM/SAM simply collects this counter information as-is with no manipulation and stores its values in the database no differently than it does for any other Windows Performance Counter. Below is an example from my workstation monitoring the rtvscan process through the Windows Performance Counter.  Microsoft describes this counter as such:

% Privileged Time is the percentage of elapsed time that the process threads spent executing code in privileged mode. When a Windows system service is called, the service will often run in privileged mode to gain access to system-private data. Such data is protected from access by threads executing in user mode. Calls to the system can be explicit or implicit, such as page faults or interrupts. Unlike some early operating systems, Windows uses process boundaries for subsystem protection in addition to the traditional protection of user and privileged modes. Some work done by Windows on behalf of the application might appear in other subsystem processes in addition to the privileged time in the process.

Process Monitoring Privleged Time.jpg