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I'm self studying for a server+ cert and ran into this paragraph. Am I right that CPU time is a set of ticks utilized, the CPU Capacity is the total capacity, and the CPU usage is the percentage of ticks:capacity?
I have been making notes from this chapter, and the more I get into it the more I seem to find things like this that seem slightly off.
Does anyone have a physical copy of the 2ed McMillan CompTia Server+ study guide I can compare against? I feel like someone is messing with me.
You are correct. Here’s a thread on how CPU usage is calculated:
https://stackoverflow.com/questions/3748136/how-is-cpu-usage-calculated
It’s basically (CPU time of the process) / (clock time), or (CPU time)/(clock time * number of hardware threads), depending on how it’s reported.
Note that there’s are some complications here, like the time “wasted” context switching or running the OS.
Thanks, good thread. I'm not sure if that's one I referenced to confirm what I suspected, but it is very clear.
Sounds about right...
Cpu time is the time your process actually uses the cpu to process things, rather than waiting.
It's often shown as a percentage in top and other performance monitors. So 10% means it's spending 1/10th of the time actually calculating things
Try elaborating on what "CPU Capacity is the total capacity" means and I think that'll get you the rest of the way to understanding this topic.
Above it says that CPU usage is the total capacity of the CPU to perform work. When I say CPU capacity is the total capacity, I mean in ticks or seconds, depending on the measurement.
What I'm struggling with is that the text says that the CPU time is a subset of the usage expressed as a percentage. It seems to me that it is incorrectly identifying CPU usage as CPU capacity.