Re: [Xen-devel] System time monotonicity

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 26/3/07 21:04, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:

>> Small backwards time deltas are possible from the current time code. You'll
>> have to filter them out yourself if you can't deal with them. We could add
>> extra code in Xen to stop this happening for any individual VCPU
> 
> Some instrumentation indicated that we had cross-VCPU jitter of
> significant deltas, ~18us at worst. Though the instrumentation wasn't
> completely reliable so that might not be accurate.

I should add that time synchronisation is currently broken in xen-unstable,
and has been for about two weeks. I just checked in a patch (based on one
from Jan Beulich) to fix this (changeset 14573:ba9d3fd4ee4b).

 -- Keir


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