I am trying to right-size a vm.
i have one vm running 8vcpus in my host.
My host has other workloads and has dual 12 core cpus.
For this VM, ESXTOP shows a value of 5 - 8 for %rdy which is above what you want to see.
Esxtop refreshes every 5 seconds
vcenter performace summation refreshes every 20 seconds but reads about 1500. This is about the same as a esxtop reading of 3.
There is No costop happening at all.
Great.
That all makes sense.
IF the %rdy number was higher say.....above 5 which is a threshold KPI, but there was no costop happening would it still affect performance? I guess i am trying to sort out when i have too many vcpus allocated to a vm. Clearly you want that number below 5 and definitely below 10 but if costop is still at 0, is there a problem? Clearly the vcpus are still having to wait to be scheduled, hence the number being high. I know costop is a bad thing for sure especially once that number gets above 3. I know %rdy is bad once it gets above 5 and 10 is a horrible number to see.
In my test then, my %rdy is showing 5-8% with an average value of 1500 summation. I dont see any performance issues. SHould i?
Also....
I have been trying to use vmcalc.com to calculate some realword numbers but i think it is calculating incorrectly.
For example if you put in my numbers and vcpu numbers
realtime
1500
8 vcpus
it calculates the %rdy as .94??
This is a long ways from the 8 i am showing live in esxtop.
That is confusing. Perhaps this calculator isnt accurate or no longer working properly.
If i change the vcpu value to 1, then it shows my %rdy as 7.5 which is correct. I dont have 1 vcpu though.....i have 8. Either i am not reading this calculator right or it is wrong. At any rate, it is an external calculator on a website and not my actually numbers shown in my environment so i will assume it is just wrong unless i am reading it wrong.
I have since dialed my vcpus back to 6 in my vm which brought my %rdy down to about 3 in this vm or 600 summation. This seems to be the better choice as to the "right size" for this vm.