What does CPU Usage actually measure?

[DragonNOA1]

Does it measure how full the pipelines are or what? I have no idea. Just talking about simple task manager and it's CPU Usage monitor. TIA

 

[psychosonik]

I would assume that the CPU (ignoring power-save settings) runs at a constant clock speed. The usage would measure how many of those clock cycles are being populated with instructions vs the speed... a simple fraction. Of course HT and Multi-core probably complicate that horribly...

Does it measure how full the pipelines are or what? I have no idea. Just talking about simple task manager and it's CPU Usage monitor. TIA

 

[Papa-Ming]

Does it measure how full the pipelines are or what? I have no idea. Just talking about simple task manager and it's CPU Usage monitor. TIA

Well just basic; CPU Usage measures time taken to execute processes.

First you have a program....program is read into ram....executed by the system kernel....executing the program is a " process "

The Performance tab real time moitor in Task Manager is showing the amount of current processor usage, expressed as a percentage of total capacity.

If you look at the Processes Tab, it shows the percentage of elapsed time that the process used the CPU to execute instructions for each process.

The Task Manager checks the counts of each task once each second and computes the CPU utilization for that period.

The System Idle task , found under your Processes Tab, is a task that runs whenever there is nothing else to do. Subtracting this number from 100 shows how busy the system is, which appears as the "CPU Usage"

Clear as mud right?

gl

 

[DragonNOA1]

Well just basic; CPU Usage measures time taken to execute processes.

If you look at the Processes Tab, it shows the percentage of elapsed time that the process used the CPU to execute instructions for each process.

So it measures time?

The Task Manager checks the counts of each task once each second and computes the CPU utilization for that period.

So it measures counts? What are counts?

Clear as mud right?

Very.


So for every second, the CPU Usage is shown as a percentage of some total capacity. I understand if it measures free registers, or how full its pipeline is, but measuring used processing power? I still don't understand what that is.

 

[Papa-Ming]

So it measures time?

So it measures counts? What are counts?

So for every second, the CPU Usage is shown as a percentage of some total capacity. I understand if it measures free registers, or how full its pipeline is, but measuring used processing power? I still don't understand what that is.

In real life use CPUs rarely do one thing at a time and in just one clock cycle. And certainly not from brand to brand and platform to platform.

But If we think of the “ total capacity " you mentioned as the total rated megahertz of your cpu.... and we know that clock ticks ( the interrupt received from interrupt timer )... and millions of clock ticks per second = megahertz.... and that most modern processors include the counter register that counts CPU clock cycles....then “measuring time” taken to execute each process running.....then the number of processes running at the same time...is a method of “ measuring used processing power.”

And with that, I’ll say good night. Because I’ll never come -up with a sentence like that again.

gl