High CPU Ready times being reported in vCenter
I had an issue today where the performance counters in vCenter were reporting a high CPU Ready time and the longer stats period the higher the number. In some cases it was reporting 1130ms but I wasn’t having any performance issue.
I decided to dive down into ESXTOP and the results were completely different. ESXTOP was reporting 0.5 or under for the CPU Ready time (RDY%) which is more than acceptable (VMware recommend anything under 10.0).
After going back and forth between ESXTOP and vCenter and asking some Colleagues I noticed something in the vCenter performance counters under the column “Roll-up” which said “Summation”. This was a bit odd so after some goggling I cam across the VMware KB 2002181 which explains that the information in the vCenter performance counters is different to that in ESXTOP and how you can convert the “Summation” into a “Percentage” figure in order to get a result based on a percentage which is what ESXTOP is showing. The calculation depends on if your looking at the past day, week, month etc so I would recommend reading the article for the full how to.