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How is CPU % in Performance tab of Task Manager determined

Priya Jagyasi 21 Reputation points
2024-11-12T16:50:38.8733333+00:00

I am looking to understand how is CPU% determined in Task Manager. I am observing a difference between CPU% in perfmon tool using % Processor Time counter. Please see attached snapshot.

Which one is correct? What is causing the difference? Screenshot (7).png

Windows 10
Windows 10
A Microsoft operating system that runs on personal computers and tablets.
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Windows Performance Toolkit
Windows Performance Toolkit
A collection of Microsoft performance monitoring tools that produce in-depth performance profiles of Windows operating systems and applications.
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Windows 11
Windows 11
A Microsoft operating system designed for productivity, creativity, and ease of use.
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  1. Castorix31 86,046 Reputation points
    2024-11-13T07:58:09.5766667+00:00

    I'm not 100% sure, but, from my tests on Windows 10, Task Manager seems to concatenate times from each process

    (NtQuerySystemInformation with SystemProcessInformation with SYSTEM_PROCESS_INFORMATION structure)

    Perfmon uses Performance Counters

    Task Manager uses them for GPU ("\GPU Engine()\Utilization Percentage"* and others, but apparently not for CPU (but to be confirmed..))

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