What CPU usage reflects the true picture?
I am running a multi-threaded Java application on Ubuntu. I want to see the CPU usage.
The read I've seen from Performance Monitor is about 42% over time. Does this mean that most processors are underutilized? I have 8 cores.
However, if I look at it in the "top" command, it shows that my Java application is using% 300 processor (one PID).
What is the true picture of my processor usage? I want to see if my Java application helps in threading use.
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By default, the top part of Linux runs in what is called IRIX mode.
With IRIX mode enabled, 1 fully usable core is 100% and 3 cores are 300%. With IRIX mode disabled, 1/8 of the fully used kernel is 12.5%. This means that it shows more than 300% at the top and 40% in the "System Monitor".
You can switch IRIX mode while the upper part is working with Shift + i . This will make the numbers match.
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