wrong CPU utilization

[Yuvraj Mann]

when playing assassin's creed odyssey task manager shows 99% CPU utilization but hwmonitor and rivatuner only shows around 80% cpu usage. why it's happening and which one i should trust?

[191x7]

Which CPU?

[Yuvraj Mann]

i5 8400

7 minutes ago, 191x7 said:

Which CPU?

 

[191x7]

33 minutes ago, Yuvraj Mann said:

i5 8400

 

6 cores, low clockes, I'd say trust the task manager and its 99%.

[unclewebb]

The Windows 10 Task Manager CPU Utilization data has been bugged for a long time.  Surprising that more people have not noticed this bug.  Here is an example.

 

 

The TS Bench has loaded 4 threads which is putting a consistent 50% load on the CPU.  Throw in another 1% CPU load for all of the Windows background tasks and ThrottleStop reports a total load of 51.0%.  That is correct.  The Task Manager is reporting CPU Utilization at 72%. 

 

I am not sure what that number means but it is not a good indication of the load on your CPU.

 

In the Task Manager, click on the Details tab.  On my laptop, it shows the correct 50% value for the TS Bench test load.  

[Mick Naughty]

Need to check per core but chances are the cpu is struggling. 

 

Same problem when I play my game. 

[Mira Yurizaki]

34 minutes ago, unclewebb said:

I am not sure what that number means but it is not a good indication of the load on your CPU.

CPU utilization in Task Manager simply means "100% - System Idle Process CPU %"

 

I don't know what TS Bench uses to measure its % Utilization.

[unclewebb]

57 minutes ago, Mira Yurizaki said:

CPU utilization in Task Manager simply means "100% - System Idle Process CPU %"

Here is the problem.  The TS Bench is fully loading 4 out of 8 threads which produces a very consistent 50% load.  The Task Manager Details tab gets this right.

 

 

While this test is running, when I switch over to the Performance tab, the CPU Utilization is being reported at a consistent 72%.  That data is wrong.  

 

 

1 hour ago, Mick Naughty said:

Need to check per core

When I switch to the per core data, it still shows the incorrect 72% number.

 

Edit - Here is what Windows seems to be doing.  The turbo boost multiplier on this CPU is 34 and the default multiplier is 24.  Windows takes the 51% actual load and multiplies it by (34/24) and that equals approximately 72%.  The data being graphed should not be used for any purpose.  

 

Here is the exact same load with Turbo Boost disabled.  Now the CPU is running at the default 24 multiplier and now the Windows Task Manager graph is finally reporting correctly.

 

 

 

The Core i5-8400 has a low Processor Base Frequency of only 2.80 GHz.  That is why @Yuvraj Mann is seeing the exact same problem.  

https://ark.intel.com/content/www/us/en/ark/products/126687/intel-core-i5-8400-processor-9m-cache-up-to-4-00-ghz.html

 

[Mira Yurizaki]

54 minutes ago, unclewebb said:

 The data being graphed should not be used for any purpose. 

I don't think it's helpful to say this if we don't know exactly what the data is, but can only surmise what it might be derived from based on observation. So here's what Microsoft says about the matter:

 

Quote

Symptoms

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Starting with Windows 8, a change was made to the way that Task Manager and Performance Monitor report CPU utilization. With this change, CPU utilization may appear to exceed 100% when the system is under a heavy load, especially when capacity is boosted by Intel Turbo Boost.  

Cause

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This change affects the way that CPU utilization is computed. The values in Task Manager now correspond to the Processor Information\% Processor Utility and Processor Information\% Privileged Utility performance counters, not to the Processor Information\% Processor Time and Processor Information\% Privileged Time counters as in Windows 7.

More Information

---

The difference between the two counter types concerns how they measure the actual work that the processor performs. The “time”-based performance counters measure the percentage of time that the processor is busy, whereas the “utility” performance counters measure how much work the processor actually performs. The utility performance counters take into account the processor performance state and Turbo Boost-based enhancements to measure and normalize the work that's being done by the CPU.

This change was intended to provide a more accurate representation of how much work the system is handling, and the utility counters do just that. A processor that’s running 50% of the time and clocked down to 50% frequency performs only half the work of a processor that’s running 100% of the time at 100% frequency. Before this change, under the time-based performance counters (used in Windows 7 Task Manager), those two processors clocked differently. Both appear to be doing the same amount of work: 100% of their capacity. With the redesigned Task Manager, the first processor is shown to be running at 50% capacity, whereas the second processor is shown to be running at 100% capacity. And Turbo Boost drives the processor above 100% of its nominal speed, and allows the processor to exceed 100% capacity.

 

It's probably important to note two things:

• The tab's name is Performance. I think that should imply something about what you're looking at.
• Turbo boost is not a guarantee. Base clock is a guarantee, at least as long as the basic electrical and cooling requirements are met. So I would argue it's reasonable for Microsoft to say % utilization in the Performance section is CPU time the process has multiplied by the ratio of the two clock speeds. After all, if a CPU is clocked at 50% higher than base clock, then performance wise it is doing say 50% more work. Though I imagine Microsoft got tired of getting calls asking why CPU % was higher than 100% and capped it, as this isn't the case with top on Linux (though top uses logical processor count times 100% rather than a ratio of the core clock)