VMs CPU issues

[Petersaints]

Hello all,

Need some help to find what is the cause of the % of CPU readiness above 5%, and the CPU at 100% on the operating system of the VMs.

So, physical memory of the 2 esxi hosts on version 6.7 was replaced. The original ones work at 2400MHz but the new ones are at 2666MHz (not according the vendor).

The state of the cluster is:

ESXTOP info:

Could this issue be related with the physical memory?

Thanks.

Regards.

[fabio1975 · Accepted solution]

Ciao 

I don't think it's completely related to memory.
Did you have any problems before the change? Are you using NUMA?
I don't know the applications that run on the VMs but looking at the data you reported there could be (in my opinion and in my experience) a relationship problem between the vCPUs and the physical CPU.
Normally a high vCPU ready value means the VM has a long wait to access physical CPU usage.
In some cases you can reduce the performance degradation by decreasing the number of vCPUs in the VMs.
More information in this link (which although it is old in the past has helped me a lot).

5.8 Determining an Appropriate vCPU-to-pCPU Ratio (vmware.com)

At least that's my opinion 🙂