Perf-Alert: Plugin - CPU-usage is per core

KPS

Hi!

I am using the perf-alert-plugin to monitor, if a VM is exceeding CPU usage.
But: The plugin seems to alert if:

A VM with 16 cores has 1 core at 100%
--> VM CPU-load is at 6,25% (not critical)

--> As this is not an issue: How can I set it up to only alert, if the usage of the whole VM exceeds e.g. 95%?

Best wishes
KPS

olivierlambert

Hi!

I'm not sure to get it

KPS

@olivierlambert
The alert is already triggered, when ONE vCore is at >95%
IMHO, it should trigger, when the VM usage exceeds 95% on all its cores

olivierlambert

Just to double check I get it:

You configure the perf alert plugin to report VM usage at more than 95%
You have a VM with 16 cores having only one core at 100%, the rest is almost idle.
You do NOT want to be alerted in that case, only if ALL cores are beyond 95%

Is that correct?

KPS

@olivierlambert
Correct - nearly…
When the total usage is >95% inside the vm

olivierlambert

Not sure to get the difference between "ALL cores are beyond 95%" vs "total usage >95%", isn't the same thing?

KPS

@olivierlambert
Nearly, but no:

Take a 2-core system with

Total >95%, but not all cores >95%

olivierlambert

Ah yes, you mean the average total CPU usage then Got it, thanks!

edit: or the sum, like if you have 8 cores, 800% would be the max and the threshold will be 760% (equivalent to 95 per 100)

olivierlambert

@Bastien-Nollet can you check the current logic for CPU alerts? I thought initially it was like @KPS described

Bastien Nollet

olivierlambert

Okay so it will be more logical to use the same logic than with the Load balancer, where we compute a total of all vCPUs