CODEWITHSUNDEEP
javalinuxmultithreadingubuntucpu-usage
user697911
user697911

Reputation: 10561

Which CPU usage reflects the true picture?

I am running a multi-thread Java application on Ubuntu. I want to watch the CPU usage.

The reading I saw from "System Monitor" is around 42% over time. Does this mean most of the CPUs is not fully utilized? I have 8 cores.

However, if I watch it in 'top' command, it shows that my Java application is using over %300 CPU (one PID).

Which reflects the true picture of my CPU utilization? I want to see whether and how my Java application benefits the threading.

Upvotes: 3

Views: 405

Answers (1)

Pav K.
Pav K.

Reputation: 2858

By default, top on Linux runs in so-called IRIX mode.

With IRIX mode on, 1 fully utilized core is 100% and 3 cores are 300%. With IRIX mode off, 1/8 fully utilized core is 12.5%. This means in top it shows over 300% and in "System Monitor" 40%.

You can toggle IRIX mode while top is running with Shift+i. This will make the numbers match up.

Upvotes: 4

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