Platform Monitor - how does it work ?

[David Richards]

Hi - I have been asked by an application team how the Wily agent calculates the CPU Utilisation % (process) metric.

 

Is there any lower level detail available about how this component works, for LINUX OS in particular ?

[Sergio Morales Correa]

Hello Dave,

I found the below old wily kb:

 

Question: How does Linux Platform Monitor calculate the CPU utilization?   

Answer: Linux Platform Monitor calculates the CPU usage by the following approach.

 

    Utilization %(Process)

    It uses getrusage() to get usr and sys CPU time in milliseconds within 1 sec. Then it calculates (usr + sys) / 1000 for the process CPU utilization.

 

    Utilization % (aggregate)

    It reads the CPU time for usr, sys, wait, and idle from /proc/stat. Then it calculates (usr + sys) / (usr + sys + wait + idle) for the aggregate CPU utilization.

 

I hope this helps,

Regars

Sergio

[David Richards]

Thanks Sergio, I will pass it on. Cheers

[David Richards]

This is the follow up question to CA.

 

 

Interesting. So if getrusage() returned 1000ms, Wily would call that 100%. As we can see JVMs exceeding 200% in top, does getrusage () return 2000+ms and Wily truncates this to 100%? It would be good if someone from Wily could confirm this.