CPU ready percentage for multi vCPu VMs threshold

[vAdmin]

Hi,

I'm trying to get some understanding as to how to calculate VM CPU Ready based on this white paper as best practice on page 5:

Key Metrics to Measure and Monitor

Ready (%RDY)

- % time a vCPU was ready to be scheduled on a physical processor but couldn’t due to processor contention

- Recommended Threshold: 10% per vCPU

Assuming I'm using ESXTop to get the %value, does that means if the CPU Ready % percentage for:

• 1x vCPU VM should not be larger than 10%
• 2x vCPU VM should not be larger than 20%
• 4x vCPU VM should not be larger than 40%
• 8x vCPU VM should not be larger than 80%

is that my understanding correct?

Source: http://docs.media.bitpipe.com/io_10x/io_107330/item_605784/Basic%20VMware%20vSphere%20Performance%20Guide_201211.pdf

[Davoud Teimouri]

Hi,

I think and as I know, CPU %RDY calculating for all VM CPU not for a core.

So your CPU ready threshold is 10% for average of all cores %RDY.

[vfk]

Hi, your understanding is correct, the value displayed is sum of #vCPU configured, you can expand the VM worlds with e and supply for the groupID for the VM.  This will show CPU ready time for the individual vCPU.

[vAdmin]

Cool, so in this case is there any formula to read or interpret the VM CPU Ready from vSphere console? because from the vSphere console I can only see in milliseconds instead of percentage.

[Scott Norris]

(CPU summation value / (<chart default update interval in seconds> * 1000)) * 100 = CPU ready %

is how we turn it into a percent

so if your seeing 5000 ms cpu ready in the realtime chart then we would go

(5000/(20*1000))*100 = 25%

if we then had 4 vCPUs we would 25 / 4 = 6.25%

Cheers

[vAdmin]

Ah I see,

I've found this KB article here: VMware KB: Converting between CPU summation and CPU % ready values which shows the update value charts.

Thanks