Re: recommended clock source

Dor Laor
2009-08-03T08:30:59Z

On 08/03/2009 11:11 AM, Antoine Martin wrote:
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> Hi,
>
> Dor Laor wrote:
>> On 08/03/2009 04:52 AM, Kent Tong wrote:
>>> Hi,
>>>
>>> It seems to be an unsettled issue, but, would any kind soul suggest
>>> the current
>>> best practice for setting the clock in Ubuntu Linux and Windows guests?
>> For Linux the best source clock is the kvm pv clock (exist from 2.6.27
>> and above).
> # qemu-system-x86_64 -clock ?
> Available alarm timers, in order of precedence:
> dynticks
> hpet
> rtc
> unix
>
> I see no "pv clock"...
> Which one should I use then?
> Did I miss a ./configure or .config option?

No, we were talking about different clocks.
I was explaining the guest source clock while you wanted some info for
the host-qemu clock.

You can use the default - dynticks. hpet and rtc might be good if you
need a fine grain granularity on older < 2.6.24 host kernels.

>
> Cheers
> Antoine
>
>> For windows, standard acpi HAL uses the rtc clock by default. As long as
>> you use the -rtc-td-hack it won't drift.
>>
>> When the tsc is not stable on the host or the host cpu might get into
>> deep sleep state (c2), you better use another source clock in the guest
>> - for windows it should be the pmtimer (using the boot.ini).
>>
>>> Thanks!
>>>
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