CPU ready spikes & Host Power Management

We just observed some strange frequently occurring CPU ready spikes in our environment (screenshot).

cpu ready spikes

This effect occurred very frequently on each virtual machine. What caused it?

-> The Host Power Management mode which was balanced. After setting it to high-performance the spikes disappeared.

I know this might have to do with the specific hardware we are using, but since I heard about such effects from time to time, think about disabling the power management mode on the ESXi once you observe strange performance symptoms. IMO server are deserving high performance and nothing less 😉

I will change my mind once I have measured the financial benefit that might occur with the balanced power management mode. So if you have any concrete facts and number. Please post it here.



1 Comment

  1. Regarding the changes in Ready time you see when changing power management settings: I’m familiar with HP ProLiant hardware, but I suspect other vendors do something similar. HP ProLiant servers have a feature called ProLiant Power Regulator, which – by default – is set to “Dynamic Power Savings”, allowing logic in the server hardware to control CPU power states.

    This default was fine for a few years ago when many operating systems did not support APM (advanced power management) with default drivers, but not really the case anymore today. As of ESX 4.1 (which supports APM), the recommended setting for HP Power Regulator is OS Control, which allows the operating system to control CPU power states. Having HP Power Regulator on OS Control and vSphere Power Management on Balanced is generally the optimal configuration.

    Have a look at the following references:
    KB1018206: Poor virtual machine application performance may be caused by processor power management settings
    vExperienced Blog: Is the HP power setting impacting your performance?
    Power Regulator for ProLiant servers

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