vSphere 6.0 Performance Metrics – What is CPU Readiness?

I haven’t seen this in any announcement, but there is a new performance metric in vSphere 6.0 called CPU Readiness which is according to the description:

Percent of time the virtual machine is unable to run because it is contending for access to the physical CPU(s).



Isn’t that the well-known Ready value? Yes, but there was a mismatch. In vCenter’s performance chart the CPU ready value was displayed as time in milliseconds while esxtop displays CPU ready as percentage.

The problem was that from having ready times in milliseconds, it was hard to tell whether it is a good value or not. To get better to understand percentages you were limited to ESXTOP (%RDY) or non intuitive formulas.

This has been changed in vSphere 6.0 where you now see both, ms and %:

You can also access cpu.readiness.average with PowerCLI:

PowerCLI #> Get-Stat -Stat cpu.readiness.average -MaxSamples 5 -IntervalMins 5

MetricId                Timestamp                   Value Unit     Instance
--------                ---------                   ----- ----     --------
cpu.readiness.average   26.03.2015 21:59:40          1,17 %
cpu.readiness.average   26.03.2015 21:59:20          0,96 %
cpu.readiness.average   26.03.2015 21:59:00          0,95 %
cpu.readiness.average   26.03.2015 21:58:40          0,81 %
cpu.readiness.average   26.03.2015 21:58:20          0,99 %


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