Re: [Qemu-devel] kvmclock, Migration, and NTP clock jitter

[Mohammed Gamal]

On Thu, Jan 15, 2015 at 06:27:54PM +0100, Paolo Bonzini wrote:
> 
> 
> On 15/01/2015 17:39, Mohammed Gamal wrote:
> > The increase in the jitter and offset values is well within the 500 ppm
> > frequency tolerance limit, and therefore are easily corrected by
> > subsequent NTP clock sync events, but some live migrations do cause much
> > higher jitter and offset jumps, which can not be corrected by NTP and
> > cause the time to go way off. Any idea why this is the case?
> 
> It might be fixed in QEMU 2.2.
> 
> See https://lists.gnu.org/archive/html/qemu-devel/2014-09/msg01239.html
> 
> Paolo

Hi Paolo,

I did try to backport these patches to qemu 1.2. However, migrations 
resulted in *higher* jitter and offset values (i.e. in the order of 100+ ppm).
I am not sure if I've done the backporting correctly though. Here are my
patches on top of the qemu 1.2 stable tree.

backport.patch
Description: Text Data