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Here is the issue: SLES 10 SP1 guest is running on HyperV. I need accurate timekeeping on this box, so I have applied these kernel parameters (which were proven to work on other identical SLES 10 SP1 guest) to boot loader configuration:

clock=acpi_pm divider=10

And of course, NTP service is on, time synchronization between hypervisor and guest is off.

After that, time is kept precisely, but I ran into dramatic increase of CPU consumption by the system. As soon as I remove clock=acpi_pm parameter, time drift is back but CPU consumption is normal.

I do need correct time on this box. And I have another box where this value of clock parameter works without any issues.

Does anyone have an idea of how to keep time correct while not impacting CPU that much?

Thank you all.

anenvyguest
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2 Answers2

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VMware recommends a slightly different set of parameters for SLES 10 SP1:

clock=pmtmr
hpet=disable

I normally run only Windows guests under Hyper-V, so I am not sure whether this is equally relevant to your environment. It is certainly worth a try.

Skyhawk
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3

Simple: DO NOT VIRTUALIZE.

Virtualization per definition has time skew. High precision software does not work well with virtualization. I have a similar system here (telling me every hour it synced by 36ms) getting a constant 100 packet per second or so data stream to keep it in sync.

Simply did not work under virtualization. Virtualiaztion Hyper-Visors are NOT real time capable at this moment.

Skyhawk
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TomTom
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