Re: [PATCH] Drivers: hv: util: Implement Time Synchronization using host time sample

From: Sitsofe Wheeler
Date: Thu Sep 25 2014 - 02:07:56 EST

On Tue, Sep 23, 2014 at 09:56:10AM +0200, Olaf Hering wrote:
> On Tue, Sep 23, Thomas Shao wrote:
> > In current hyper-v time sync service,it only gets the initial clock time
> > from the host. It didn't process the following time samples. This change
> > introduced a module parameter called host_time_sync. If it is set to true,
> > the guest will periodically sychronize it's time with the host clock using
> > host time sample. By default it is disabled, because we still recommend
> > user to configure NTP for time synchronization.

You [Microsoft?] do? Can you link to public sources where is this stated
please? I don't see any mention of doing this on .. The only
official Microsoft information with respect to Hyper-V guest time
synchronisation I've seen has been for Windows guests but perhaps I've
looked in the wrong places.

The reason I ask is because regular ntpd is not enough to discipline a
Linux Hyper-V guest's clock. So much drift can occur under load that
ntpd can't bring the clock under sync. For now, I've been using Chrony
which has a higher tolerance for correcting drifting clocks. I'm not the
only one seeing this either (see

It would be good to something official about this issue as it is painful
when happens.

Sitsofe |
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