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Re: [Qemu-devel] kvmclock, Migration, and NTP clock jitter
From: |
Mohammed Gamal |
Subject: |
Re: [Qemu-devel] kvmclock, Migration, and NTP clock jitter |
Date: |
Fri, 16 Jan 2015 11:21:20 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
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