Re: Clock jumps

[Zachary Amsden]

On 05/27/2010 12:12 PM, Bernhard Schmidt wrote:
> On 27.05.2010 23:53, Zachary Amsden wrote:
>
> Hello Zachary,
>
> > I have server side fixes for this kvm-clock which seem to give me a
> > stable clock on this machine, but for true SMP stability, you will need
> > Glauber's guest side changes to kvmclock as well. It is impossible to
> > guarantee strictly monotonic clocksource across multiple CPUs when
> > frequency is dynamically changing (and also because of the C1E idle
> > problems).
>
> Is all this relevant only when the host is on TSC? Because I have seen 
> these jumps when the host was on HPET and the guests were using 
> kvm-clock.

It doesn't matter what the host uses (although the host on TSC with 
unstable TSC can make things worse), tsc and kvmclock sources in the 
guest will be unstable regardless.
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