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E8500
Contributor
Contributor

How to set Power.CpuPolicy to "dynamic"?

I've upgrade my ESXi 3 server to ESXi 4.

I'm trying to change CPU power management policy to utilize Dynamic Voltage and Frequency Scaling(DVFS) as discrived in vSphere Resource Management Guide.

It states that to set the CPU power management policy for DVFS, set the advanced host attribute Power.CpuPolicy to "dynamic".

However, I tryed to to set Power.CpuPolicy from vsphere Client, it made a error dialog, "The value entered is not valid. Enter another value."

I would like to know how to set Power.CpuPolicy to "dynamic"?

Thank you

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AndreTheGiant
Immortal
Immortal

Do your hardware support this feature?

Sometimes you must enable in BIOS.

Andre

**if you found this or any other answer useful please consider allocating points for helpful or correct answers

Andrew | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
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E8500
Contributor
Contributor

Thank you for your answer.

I've checked the hardware spec. and BIOS settings.

I confirmed that CPU and motherboard have Enhanced Intel speed step technology, and the BIOS setting of it is enabled.

CPU: Core2Duo E8500

Motherboard: Elite G33T-M2

Have you set Power.CpuPolicy to "dynamic" successfully?

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AndreTheGiant
Immortal
Immortal

Have you set Power.CpuPolicy to "dynamic" successfully?

Not yet, cause I'm not using VS4 in production.

And in my testing environment I do not have CPU with this function. Smiley Sad

Andre

**if you found this or any other answer useful please consider allocating points for helpful or correct answers

Andrew | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
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dorofeev
Enthusiast
Enthusiast

If you got an error when setting Power.CpuPolicy property to "dynamic", then it means that your system does not have proper support for DVFS. What do you see under "Configuration" tab when you click on "Processor" section? There should be new field called "Hardware Support" which should say what type of power management hardware support was detected. Also, make sure your server has power management enabled in the BIOS. In general, power management (DVFS) is supported on Intel Core family of CPUs and on AMD Greyhound/Barcelona and newer.

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E8500
Contributor
Contributor

Thank you for your answer!

I've update the BIOS, then ESXi recognize Enhanced Speed Step functionality on the configration tab.

Of course, I've successfully set Power.CpuPolicy to "dynamic".

However, total wattage of my server doesn't decrease, even all of VMs are suspended.:(

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LucasAlbers
Expert
Expert

I have 3 dell r905 servers running esxi and 4.0 with dynamic policy set. 4.0 uses 40% less power (watts) at it's current idle load.

esxi 3.5: 420 - 429

esxi 3.5: 385 - 399

esxi 4.0 with dynamic power policy: 259 - 280.

(259 * 2) / (420 + 385) = 0.643478261

That is amazing, and trivial to enable.

YMMV depending on your load.

dorofeev
Enthusiast
Enthusiast

That's not unexpected at all. Depending on the processor type and model, decreasing CPU frequency when processor is idle may or may not provide any power savings. Many recent Intel processors support C1E state, which automatically reduces core frequency when the whole package is idle (all cores are idle). This means that reducing frequency using DVFS algorithm in ESX when package is relatively idle is not going to help since the hardware is already doing it. However, even on those systems, you can still expect to see some power savings when there is some load. C1E only works in cases when packages are almost completely idle, and DVFS algorithm in ESX can help to save power when load is somewhere below 60% (which is a configurable threshold by the way). DVFS will continously monitor CPU utilization and make sure that core frequency is not unnecessarily higher than what is currently required. So, for example, if CPU utilization is 25% when CPU is running with its highest frequency, ESX can reduce frequence almost in half thus potentially increasing CPU utilization to 50% but still leaving enough headroom for sudden changes in CPU load. DVFS algorithm used in ESX is very conservative, and it aims to save power while not affecting performance. Hope this helps.

dorofeev
Enthusiast
Enthusiast

Lucas: That's really good to hear! Can you please tell what processors do these Dell R905 systems have? Do they have quad-core AMD Barcelonas?

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LucasAlbers
Expert
Expert

quad core amd opteron 8380

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E8500
Contributor
Contributor

To be correct, my Intel Core2Duo E8500 processor server decreases power consumption 1 or 2% as follows.

static: 123W

dynamic: 121W

4VMs working at 5% total cpu usage.

I understand that Core2Due E8500 do power saving very well by itself even ESXi is "static".

I know 1 or 2% is very important for huge instragions like a datacenter.

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dorofeev
Enthusiast
Enthusiast

Correct. The C1E enhancement is doing pretty good job of saving power on CPUs that are mostly idle. If you're interested, try disabling C1E in the BIOS (some systems let you do that) and measure idle power with C1E off.

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LucasAlbers
Expert
Expert

What happens if you turn all the vm's off?

Then what does the power usage show?

Are you limiting the vm's to only run on a subset of the cpu's?

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E8500
Contributor
Contributor

If I turn all of VMs off, the power usage is down to 115w and the difference between "dynamic" and "static" disappear.

I don't limit cpu resource for any VMs.

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